Dynamic reconfiguration of a system monitor (DRPORT)

ABSTRACT

Method and apparatus for a dynamically reconfigurable system monitor ( 20 ) are described. A system monitor ( 20 ) has registers ( 206 ) accessible via a reconfiguration port ( 201 ). At least one of the registers may be dynamically reconfigured via the reconfiguration port ( 201 ) to select a channel to be monitored or to store an alarm value to be used in monitoring by the system monitor ( 20 ). Additionally, the system monitor ( 20 ) may be embedded in a columnar block architecture.

FIELD OF THE INVENTION

One or more aspects of the invention relate generally to testing anintegrated circuit having a system monitor and, more particularly, to asystem monitor embedded in a programmable logic device.

BACKGROUND OF THE INVENTION

In semiconductor industry, integrated circuits continue to use smallergeometries, lower supply voltages, and higher integration. Theseintegrated circuits consequently have higher current densities andincreased power dissipation. Accordingly, monitoring of environmentalconditions, such as temperature, at the system or circuit board level isnow done at the integrated circuit level.

Thermal control circuits used to ensure an integrated circuit does notexceed a factory defined temperature limit have been included inmicroprocessor integrated circuits. However, having thermal control doneby a microprocessor, which may be a central processing unit of a system,adds overhead to processing functionality that may reduce systemperformance. Accordingly, monitoring may be offloaded to a processor ordedicated monitor. However, conventionally, such offloading involved athree or more additional integrated circuits to provide sufficientadditional input/output and busing to support a number of sensors, aswell as driver software. More recently, single chip sensor monitors havebeen developed. However, such single chip sensors heretofore have notprovided a substantially complete single chip solution owing toconfiguration limitations, among other limited features.

Besides monitoring environmental conditions or physical characteristicsof a system, it is useful to be able to obtain test data associated withsuch monitoring. Joint Test Action Group (“JTAG”) functionality is aknown way for conducting a boundary scan or otherwise digitally testingan integrated circuit. Additionally, the Institute of Electrical andElectronics Engineers (“IEEE”) has advocated a standard for analogboundary scanning, namely, IEEE 1149.4. Both analog and digital sensorsmay be useful for monitoring integrated circuit physical characteristicsand environmental conditions, whether internal or external to a chassis.

Accordingly, it would be desirable and useful to provide systemmonitoring in a single integrated circuit that facilitates obtainingdata obtained from an analog or digital sensor.

SUMMARY OF THE INVENTION

An aspect of the invention is a method of system monitoring, includingproviding a system monitor having registers accessible via areconfiguration port; and dynamically reconfiguring via thereconfiguration port the registers to store an alarm value to be used inmonitoring by the system monitor.

Another aspect of the invention is a method of system monitoring,including: providing a system monitor having registers accessible via areconfiguration port; and dynamically reconfiguring at least one of theregisters via the reconfiguration port to select a channel to bemonitored by the system monitor.

Yet another aspect of the invention is an integrated circuit havingcircuit blocks arranged in an array, at least one of the circuit blocksbeing for a system monitor, including: interconnect tiles disposed in acolumn; and a system monitor block disposed along a side of the columnof interconnect tiles, where the system monitor block includes an analogblock, a logic block, and a dynamically reconfigurable memory block. Thedynamically reconfigurable memory block is disposed adjacent to a firstportion of the interconnect tiles. The logic block is disposed adjacentto a second portion of the interconnect tiles. The analog block isdisposed adjacent to a third portion of the interconnect tiles.

BRIEF DESCRIPTION OF THE DRAWINGS

Accompanying drawing(s) show exemplary embodiment(s) in accordance withone or more aspects of the invention; however, the accompanyingdrawing(s) should not be taken to limit the invention to theembodiment(s) shown, but are for explanation and understanding only.

FIG. 1A is a high-level block diagram depicting an exemplary embodimentof a Field Programmable Gate Array (“FPGA”) with a “ring” architecture.

FIGS. 1B and 1C are high-level block diagrams depicting an exemplaryembodiment of an FPGA with a “columnar” architecture.

FIG. 1D is a high-level block diagram depicting another exemplaryembodiment of an FPGA with a “columnar” architecture and with anembedded processor.

FIG. 1E is a block diagram depicting an exemplary embodiment of aninternal configuration/reconfiguration (“configuration”) interface.

FIG. 2 is a high-level schematic/block diagram depicting an exemplaryembodiment of a pin-out for a System Monitor of FIGS. 1A and 1B.

FIG. 3A is a schematic/block diagram depicting an exemplary embodimentof the System Monitor of FIG. 2.

FIG. 3B is a simplified block diagram of a System Monitor of analternative embodiment of the present invention.

FIG. 3C is a block diagram of an ADC of an embodiment of the presentinvention.

FIG. 4 is a block diagram depicting an exemplary embodiment of a memorymap for System Monitor registers for system monitor registermemory/interface of FIG. 3A

FIG. 5 is a block diagram depicting bit assignments for configurationregisters of FIG. 4.

FIG. 6A is a temperature versus output code graph depicting an exemplaryembodiment of an output of an analog-to-digital converter (“ADC”) forthe System Monitor of FIG. 2.

FIG. 6B is a schematic diagram depicting an exemplary embodiment ofexternal ADC monitoring circuitry for the ADC of FIG. 3A.

FIG. 7A is a signal diagram depicting an exemplary embodiment of SystemMonitor start up timing.

FIGS. 7B and 7C are signal diagrams depicting respective exemplaryembodiments of partial configuration timings.

FIG. 8A is a signal diagram depicting an exemplary embodiment of aContinuous Sampling Mode timing.

FIG. 8B is a signal diagram depicting an exemplary embodiment of anEvent Driven Sampling Mode timing.

FIG. 8C is a lower-level signal diagram depicting an exemplaryembodiment of a System Monitor detailed timing.

FIG. 9A is a signal diagram depicting another exemplary embodiment of aContinuous Sampling Mode timing.

FIG. 9B is a signal diagram depicting another exemplary embodiment of anEvent Driven Sampling Mode timing.

FIG. 9C is a lower-level signal diagram depicting another exemplaryembodiment of a System Monitor detailed timing.

FIG. 10 is a block/schematic diagram depicting an exemplary embodimentof a portion of the System Monitor of FIG. 2 with averaging.

FIG. 11 is a block diagram depicting an exemplary embodiment of aportion of the System Monitor of FIG. 2 having a digital comparator.

FIG. 12 is a block/schematic diagram depicting a single pointtemperature calibration circuit for the System Monitor of FIG. 2.

FIG. 13A and FIG. 13B are schematic diagrams depicting exemplaryembodiments of respective unipolar and bipolar mode analog inputs to theADC of FIG. 3A.

FIGS. 14A and 14B are block diagrams depicting respective exemplaryembodiments of System Monitor floor plans for the System Monitor of FIG.2.

FIG. 15A is a schematic diagram depicting an exemplary embodiment of aclock tree for the System Monitor of FIG. 2.

FIG. 15B is a block diagram depicting an exemplary embodiment of an FPGAhaving a System Monitor of FIG. 2.

FIG. 16A is a block diagram depicting an exemplary embodiment of IEEE1149.1 Test Access Port (TAP) connections for the System Monitorregister memory/interface of FIG. 3A.

FIG. 16B is a signal diagram depicting an exemplary embodiment of aSystem Monitor TAP signal read timing for the System Monitor registermemory of FIG. 3A.

FIG. 16C is a signal diagram depicting an exemplary alternativeembodiment of System Monitor read timing.

FIG. 17A is a block/schematic diagram depicting an exemplary embodimentof an analog-to-digital TAP controller interface for capturing data.

FIG. 17B is a block/schematic diagram depicting an exemplary embodimentof a digital-to-analog TAP controller interface for generating anon-chip or off-chip analog stimulus signal.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following description, numerous specific details are set forth toprovide a more thorough description of the specific embodiments of theinvention. It should be apparent, however, to one skilled in the art,that the invention may be practiced without all the specific detailsgiven below. In other instances, well known features have not beendescribed in detail so as not to obscure the invention.

Exemplary FPGA Configurations

FIG. 1A is a high-level block diagram depicting an exemplary embodimentof a Field Programmable Gate Array (“FPGA”) 10 with a “ring”architecture. FPGA 10 is an example of an integrated circuit withsoftware configurable logic and interconnects. However, otherProgrammable Logic Device (“PLD”) integrated circuits other than FieldProgrammable Gate Arrays (“FPGAs”), including complex PLDs (“CPLD”) andother integrated circuits with configurable logic and interconnects, maybe used.

FPGA 10 includes configurable logic blocks (“CLBs”) 26, programmableinput/output blocks (“IOBs”) 22, memory, such as block random accessmemory 28, delay lock loops (“DLLs”) and multiply/divide/de-skew clockcircuits which collectively provide digital clock managers (“DCMs”) 13,and multi-gigabit transceivers (“MGTs”) 24.

An external memory may be coupled to FPGA 10 to store and provide aconfiguration bitstream to configure FPGA 10, namely, to program one ormore configuration memory cells to configure CLBs 26 and IOBs 22.Notably, IOBs 22, as well as MGTs 24, are disposed in a ring orring-like architecture forming a perimeter of IOs around CLBs 26 of FPGA10.

Additionally, FPGA 10 may include an Internal Configuration Access Port(“ICAP”) 16, an embedded processor 30, an embedded System Monitor 20with an Analog-to-Digital Converter (“ADC”). Though FPGA 10 isillustratively shown with a single embedded processor 30, FPGA 10 mayinclude more than one processor 30. Additionally, known supportcircuitry for interfacing with embedded processor 30 may be included inFPGA 10. Furthermore, rather than an embedded processor 30, processor 30may be programmed into configurable logic such as a “soft” processor 30.

Although FIG. 1A (not to scale) illustratively shows a relatively smallnumber of IOBs 22, CLBs 26 and BRAMs 28, for purposes of example, itshould be understood that an FPGA 10 conventionally includes many moreof these elements. Additionally, FPGA 10 includes other elements, suchas a programmable interconnect structure and a configuration memoryarray, which are not illustratively shown in FIG. 1A. Additional detailsregarding an example of an FPGA are described in “Virtex-II™ Pro,Platform FPGA Handbook”, (Oct. 14, 2002) which includes “Virtex-II Pro™Platform FPGA Documentation” (March 2002) “Advance ProductSpecification,” “Rocket IO Transceiver User Guide”, “PPC 405 UserManual” and “PPC 405 Processor Block Manual” available from Xilinx,Inc., 2100 Logic Drive, San Jose, Calif. 95124.

FPGA 10 is configured in response to a configuration information(commands and data) bitstream, which is loaded into a configurationmemory array of FPGA 10 from an external memory, e.g., a read-onlymemory (“ROM”), via configuration interface 14 and configuration logic12. Configuration interface 14 can be, for example, a select mapinterface, an IEEE 1149.1 TAP interface, or a master serial interface.Alternatively, with respect to external configuration orreconfiguration, FPGA 10 may be internally reconfigured through use ofICAP 16 or a dynamic reconfiguration port (“DRP”) 201 (shown in FIG. 2).A dynamic reconfiguration port is described in additional detail incommonly assigned, co-pending U.S. patent application entitled“Reconfiguration Port for Dynamic Reconfiguration”, by Vasisht M. Vadi,David P. Schultz, John D. Logue, John Mcgrath, Anthony Collins, and F.Eric Goetting, filed concurrently, which is incorporated by referenceherein in its entirety.

Configuration data is conventionally divided out into data frames.Configuration data may be loaded into the configuration memory array oneframe at a time via configuration interface 14 or ICAP 16, or insub-frame increments (e.g., one or more words, bytes, and/or bits) via adynamic reconfiguration port.

FIGS. 1B and 1C (not to scale) are high-level block diagrams depictingan exemplary embodiment of an FPGA 50 with a “columnar” architecture.FIG. 1B illustratively shows a top portion of FPGA 50, and FIG. 1Cillustratively shows the bottom portion of FPGA 50.

FIG. 12D (not to scale) is a high-level block diagram depicting anotherexemplary embodiment of an FPGA 60 with a “columnar” architecture andwith an embedded processor 30. A column of MGTs 81 may be disposed onopposite sides of FPGA 60. Programmable fabric 80, which may includeCLBs and programmable interconnects, may be used to respectively couplecolumns of MGTs 81 to columns of BRAMs 82. Programmable fabric 80 may beused to couple columns of BRAMs 82 to one another and to columns of IOBs84. This inward progression on two opposing sides of FGPA 60 of couplingcolumns may continue until a center or generally centrally locatedcolumn 83 is reached.

Center column 83 may be coupled to columns of BRAMs 82 via programmablefabric 80. Center column 83 may include function logic blocks. Functionlogic blocks may, for example, include a System Monitor (“SM”) 20, oneor more DCMs 13, one or more clock companion modules (“CCMs”), andconfiguration logic (“CFG”) 12, and one or more IOBs 22, among otherfunction logic blocks. Notably, not all function blocks have to belocated in center column 83. For example, Digital Signal Processors(“DSPs”) may be instantiated in columns of DSPs 88, which are coupled tocolumns of BRAMS 82 via programmable fabric 80. Alternatively, one ormore DSPs may be included in center column 83.

System monitor 20 may include an ADC to monitor parameters liketemperature and voltage, both internally (“on-chip”) and externally(“off-chip”). A second ADC 71 may be instantiated, for example generallyat the top of center column 83 of FPGA 60, to provide additionalexternal analog channels. Notably, a second ADC 71 may be included inFPGA 10 of FIG. 1A.

DCMs 13 may include circuits to perform clock de-skew, clock phaseshifting, clock frequency synthesis, and other clock features. CCMs 74may include circuits for phase-matched binary clock division andinternal clock jitter and skew measurement.

Configuration logic 12 includes logic used to address and loadconfiguration information into configuration memory cells, such asSRAM-based configuration memory cells, during configuration of FPGA 60from an externally supplied bitstream. Configuration logic 12 mayinclude configuration registers, boundary-scan test circuitry, such asTAP controller circuitry, and encryption or decryption circuitry used torespectively encrypt or decrypt bitstreams of configuration data loadedinto or read out of FPGA 60 as applicable. Additional details regardingFPGA 60 may be found in a co-pending U.S. patent application Ser. No.10/683,944, entitled “Columnar Architecture”, by Young, filed Oct. 10,2003, which is incorporated by reference herein in its entirety.

FIGS. 1B and 1C in combination provide a more detailed block diagram ofan FPGA 50 having a columnar architecture, though columns have beentransposed for rows. The word “tile” as used herein includes an areacomprising a) circuitry with one or more programmable functions,including memory, or fixed non-programmable circuitry, and b)programmable interconnections.

CLB tiles 43 are laid out in a two-dimensional array. In this example,each CLB tile 43 includes a portion of a programmable interconnectstructure such that at least part of the programmable interconnectstructure for FPGA 50 is formed by the various portions of the many CLBswhen CLB tiles 43 are formed together for FPGA 50. Also illustrated areblock random memory/multiplier (BRAM/Multiplier) tiles 44.

In order to provide input/output circuitry for interfacing FPGA 50 toexternal logic, IOB tiles 42 are provided along two outermost rows(e.g., top and bottom rows) of FPGA 50. In this particular example, aninput/output interconnect tile (“IOI tile”) is used to couple an IOBtile to a CLB tile. Reference numeral 41 points to one such IOI tile.IOI tile 41 is disposed between an IOB tile 42 and a CLB tile 43.

DSPs are placed in tile area 45. A generally central tile area 46 may beused for support circuitry. The support circuitry may include, forexample, DCMs 13, CCMs 74, IOBs 22, configuration logic 12,encryption/decryption logic, global clock driver circuitry,boundary-scan circuitry and System Monitor 20.

In this particular example, clock distribution circuitry is located intile areas 48 and 52. Tile area 48 is for DCM clock distribution, IOBclock distribution and H-tree row clock distribution, as well as FPGA“global” buffers (“BUFG”). Notably, H-tree clock distribution 40 may bedisposed between columns of tiles. Tile area 52 is for FPGA “global”clock distribution 58.

FIG. 1E is a block diagram depicting an exemplary embodiment of aninternal configuration/reconfiguration (“configuration”) interface 99.Internal configuration interface 99 includes a processor 30, a BRAMcontroller 93, at least one BRAM 28, an ICAP controller 96, and ICAP 16,and configuration logic 12. BRAM controller 93 and ICAP controller 96may be instantiated using configurable logic and programmableinterconnects to provide bus 95 connectivity with processor 30.Configuration interface 99 is described in additional detail in aco-pending U.S. patent application Ser. No. 10/377,857 entitled“Reconfiguration of a Programmable Logic Device Using Internal Control”,by Blodget et al., filed Feb. 28, 2003, which is incorporated byreference herein in its entirety.

System Monitor and ADC.

FIG. 2 is a high-level schematic/block diagram depicting an exemplaryembodiment of a pin-out for System Monitor 20. Notably, inverted signalsare indicated with “_b” in the signal identifier. However, for clarity,inverted signals are referred to as “signals” elsewhere herein. Withsimultaneous reference to FIGS. 1A through 1E and FIG. 2, the pin-out ofSystem Monitor 20 is further described.

Input pin 101 is for receiving an auxiliary supply voltage (V_(CCAUX))for System Monitor 20 and for interface and level translation logic.Input pin 102 is for receiving an internal supply voltage (V_(CCINT)).Internal supply voltage 102 supplies voltage for digital logic of SystemMonitor 20. Input pin 103 is for receipt of a ground for System Monitor20.

Input pins 104 through 108 are inputs from a dynamic reconfigurationport (“DRP” or “DRPORT”) 201. DRP 201 is described in more detail in aco-pending patent application entitled “Reconfiguration Port for DynamicReconfiguration”, by Vasisht M. Vadi et al.

Input pin 104 or more particularly input pins 104 are data input pinsfor a System Monitor register input. Data input 104 may be a 16-bit wideinput (i.e., 16 separate input pins for parallel input). Data inputsallow data to be written to System Monitor registers. Output pins 120are data output pins for providing System Monitor register outputs.Output pins 120 may be for a 16-bit wide data output. Data output signal120 is for reading data from System Monitor registers

Input pin 105, or more particularly input pins 105, are for receiving aSystem Monitor register address. Data address signal 105 may be 7-bitswide. Input pin 106 is for receiving a data enable signal, which is aDRP 201 enable signal. Input pin 107 is for receiving a data writeenable signal, which is a System Monitor register write enable signal.Input pin 108 is for receiving a DRP clock signal (“DCLK”), which may bea reference clock signal for read and write operations to DRP 201. Itmay also be used as the reference clock for the control logic of SystemMonitor 20. Output pin 109 is for a data ready signal for DRP 201. Dataready signal 109 may be used to indicate that data written to a dynamicreconfiguration port has been latched or that data on an output data busof System Monitor 20 is valid or otherwise may be read out.

Input pins 104 through 108 and output pins 109 and 120 collectively areDRP (DRPORT) 201. Pins 104 through 108 and pins 109 and 120 may beconnected to a programmable interconnect of a programmable logic device,such as a field programmable gate array (“FPGA”).

Accordingly, it should be understood that via DRP 201 registers ofSystem Monitor 20 may be written to or read from during operation ofSystem Monitor 20 for dynamic writes or reads. System Monitor 20includes ADC configuration, sequence and alarm registers that may bedynamically accessed for a read or write operation via DRP 201.

Input pin 199 is for receiving a configuration reset signal, which maybe used to reset logic and interface portions of System Monitor 20.Notably, System Monitor register contents are not reset by reset signal199. A logic high signal on input pin 199 resets System Monitor controllogic. Responsive to reset signal 199 being de-asserted, System Monitor20 leaves the reset state on a next positive edge of DRP clock signal108. Input pin 199 may be connected to an FPGA programmableinterconnect, such as local interconnect.

Bi-directional interface 110 is an IEEE 1149.1 TAP interface. Controlsignals may be provided via the IEEE 1149.1 interface to System Monitor20. System Monitor 20 includes a dedicated connection between dataregisters and a TAP controller state machine, where the TAP controllerstate machine is instantiated in configuration logic of the FPGA.Notably, the TAP controller state machine may be instantiated on anypost power-up configuration of the FPGA such that access to SystemMonitor data is provided. Alternatively, the TAP controller statemachine (e.g., “JTAG state machine”) may be dedicated (“hardwired”)logic, which is hardwired to System Monitor 20. Bi-directional interface110 may be used to pre-configure System Monitor 20 prior toconfiguration of an FPGA in which System Monitor 20 is located. In otherwords, dedicated connections of bi-directional interface 110 may beaccessed to configure System Monitor 20 after a host FPGA is powered upor when a host FPGA is in a power down mode. This facilitates verifyingfunctionality of a host FPGA prior to configuration thereof.

Output pin 111 may be formed using dedicated connections to a host FPGA,namely, such connections are hardwired as opposed to formed usingprogrammable interconnects. Output pin 111 is for outputting anover-temperature (“OT”) signal. OT signal 111 is coupled to FPGAconfiguration logic by dedicated wires that are not interconnect wires.Thus, such dedicated connections may remain functional even after a hostFPGA enters a power down mode. OT signal 111 may be used to send an FPGAinto a power down mode responsive to reaching a threshold temperature.However, even in the power down mode, System Monitor 20 will continue tofunction (using an internal oscillator), and reassert OT signal 111responsive to a previously overheated FPGA cooling down to a temperaturewhere it may be powered up again without significant risk to damagingthe FPGA. If the FPGA, or other integrated circuit, is beingautomatically powered down, a user would see this flag go active priorto chip power down and be able to do one or both of logging the event oractivating a safe power down.

Input pins 112 through 114 may be to dedicated connections to a hostFPGA, namely, such connections are hardwired. Input pins 112 through 114are System Monitor pre-configuration signals 271. Input pin 112 is forreceiving a configuration write signal. Configuration write signal 112may be used to place System Monitor 20 in a temperature only monitoringmode during full or partial configuration of a host FPGA. Notably,thermal monitoring may be initiated prior to configuration of the hostFPGA. Configuration write signal 112 places System Monitor 20 in a“safe” operating mode where it continues to monitor temperature or otherparameters even during FPGA configuration. In this “safe”, operatingmode, System Monitor 20 is insensitive to random changes of bits in thecontrol registers which may happen during configuration of a host FPGA.

Input pin 113 is for receipt of an initialization completed signal.Input pin 113 may be part of a dedicated connection from configurationlogic 12 of a host FPGA 10 to System Monitor 20, where configurationlogic 12 provides an initialization complete signal 113 indicating thata power-up sequence of the host FPGA has completed. Notably, thisinitialization complete signal 113 may be used as a flag to cause SystemMonitor 20 to start monitoring temperature or other analog parameters ofthe host FPGA. Examples of such other analog parameters may includepower supply voltages, power supply currents, and internal testvoltages, among others.

Input pin 114 is for receipt of a configuration/chip reset signal. Aconfiguration reset signal 114 may be asserted whenever a full-chipreset is to be undertaken. System monitor 20 may use configuration resetsignal 114 to reset portions of System Monitor logic and interfaceports.

Input pins 116, 117 and 118 may be connected to FPGA programmableinterconnects for input to multiplexer 115. Input pin 116 is for receiptof logic input for a Convert Start (“CONVST”) signal. Input pin 117 isfor receipt of a local clock input for a CONVST clock signal. Input pin118, or more particularly input pins 118, is for receipt of global clockinputs. Global clock inputs 118 may for example be 16-bits wide. Globalclock inputs 118 allow a CONVST clock to be taken from an IOB clock busof a host FPGA, which may be a differential signal having little to nojitter and little to no skew. For global clock input 118 being 16-bitswide, one of 16 possible clocks may be selected by multiplexer 115.Whether selected from input pin 116, 117 or 118, output of multiplexer115 is CONVST clock signal 157. CONVST clock signal 157 may be used todefine an ADC sampling instant for an event-sampling mode.

Interconnect resources exist throughout interconnect tiles of an FPGA toallow flexibility in routing resources. DRP clock signal 108 may beobtained from a general interconnect tile. CONVST clock signal 116, usedfor event mode sampling, may not come from an interconnect tile but maybe obtained from a clock multiplexer implemented within System Monitorblock 20.

Because of a source clock is used for reference generation for on-chipsensors, which are switch capacitor based, DRP clock signal 108 is usedfor functioning of System Monitor block 20.

Configuration memory cells of a host FPGA may be tested using a readbackoperation as described in the co-pending patent application entitled“Reconfiguration Port for Dynamic Reconfiguration”, by Vasisht M. Vadiet. al., filed concurrently

, which is incorporated herein by reference in its entirety. A separatememory interface to an embedded processor memory interface, such as ahardwired PicoBlaze or MicroBlaze, where the PicoBlaze and MicroBlazesoftcores are available from Xilinx, Inc. of San Jose, Calif., may beaccessed via memory address pins 119 and memory data pins 120. Asdescribed below in additional detail, programmable read-only memory mayoptionally be included with System Monitor 20 for access by an embeddedprocessor. The embedded processor may be used to run programs out ofsuch memory, such as averaging values, among other functions describedherein. However, if there is not sufficient area for includingprogrammable read-only memory within System Monitor 20, memory internalor external to a host FPGA may be accessed via pins 119 and 121.

Input pins 122 and 123 may be connected to dedicated interconnects of ahost FPGA. These are dedicated pins connected to package pins and arenot connected through FPGA programmable interconnects. Rather, inputpins 122 and 123 are analog inputs for an ADC and as such are ADC pins.Pins 124 through 127 may be provided as selectable pins using localdigital input/output (“IO”) pins of a host FPGA.

Pins 122 and 123 are respectively for receiving positive and negativeanalog voltage inputs. By providing dedicated external analog inputs foran ADC, pins 122 and 123 provide one differential analog input channel.

Input pins 124 and 125 are for respectively receiving positive andnegative analog voltage inputs, namely, an external analog inputchannel. There may be multiple user selectable analog input pinsexternal to System Monitor 20 which would depend in part upon the numberof external analog input channels for an ADC, as indicated as pairs ofpositive and negative voltage input analog pin pairs 124, 125 to 126,127. Though for purposes of clarity, seven external analog inputchannels are described below, fewer or more analog external inputchannels may be used. Notably, fewer or more analog input channels maybe provided by reconfiguring local digital IO's. Such analog inputchannels may be defined at or during configuration of a host FPGA.

Output pins 131 through 135 and 137 through 140 may be coupled toprogrammable interconnects of a host FPGA. Output pins 131 through 135are ADC outputs. Output pins 131 are for a data output signal of an ADC.Notably, bus width of this data bus 131 may be 12-bits. Notably, databus 131 may be 12-bits wide, with only a portion of those 12 bits beingavailable to a user for purposes of analog-to-digital conversion. Aresult of analog-to-digital conversion of analog information by an ADCof System Monitor 20 is provided as output as data output signal 131. Anongoing analog-to-digital conversion process by an ADC of System Monitor20 is indicated by output signal 135, namely busy signal 135. Forexample, for the duration of an analog-to-digital conversion busy signal135 will be at a logic high voltage and at the conclusion of such ananalog-to-digital conversion busy signal 135 will transition to a logiclow voltage.

Output signal 132 is a channel output signal. Channel signal 132indicates what channel, for example, one of five available channels, isbeing used for data output 131.

Output pin 133 is for an end of conversion (“EOC”) signal. EOC signal133 output is a voltage logic level high pulse within one period of DRPclock input 108 to indicate that a result of an analog-to-digitalconversion, including an averaging function thereof, has beentransferred to output data registers.

Output pin 134 is for an end of sequence (“EOS”) signal. EOS signal 134is a logic level high pulse within one period of DRP clock signal 108 toindicate an end of a sequence such as for a channel sequencer 222 (shownin FIG. 3A).

Outputs 137 are for alarm signals. For example, there may be sevenseparate output pins 137 for alarm signals. Alarm signals 137 are usedto indicate that measured on chip parameters, such environmentalconditions or physical characteristics of a host FPGA or a platformmonitored by a host FPGA, have exceeded alarm threshold values specifiedin alarm registers of System Monitor 20.

Output pin 139 is for an over temperature alarm signal. Over temperaturealarm signal 139 is available on a programmable interconnect of a hostFPGA in contrast to a dedicated or hardwired connection as used for overtemperature signal 111. Over temperature alarm signal 139 may go activea few milliseconds before over temperature signal 111.

Output pin 140 is for a CONVST output clock signal. CONVST clock outputsignal 140 may be derived from CONVST clock signal 157. In order to testthe output of multiplexer 115, CONVST output clock signal 140 may be fedback to a programmable interconnect via a logic created input.

Additional ports may be used for production testing. There may be twosets of scan ports, such as scan port A and scan port B for suchproduction testing. For example, input pins 141 and 146 may respectivelybe for scanned data input to port A and port B. Output pins 142 and 147may be for scan data outputs from port A and from port B respectively.Input pin 143 and input pin 148 may be for respective port A and port Bscan clock signals. Input pin 144 and input pin 149 may be forrespective port A and port B scan enable signals. Input pin 145 andinput pin 150 may be for respective port A and port B scan test enablesignals. Input pin 151 may be for a scan memory clock signal. Input pin152 may be for a scan memory write enable signal. Accordingly, pins 141through 152 are for scan test signals 276 and are connected to host FPGAthrough programmable interconnects.

Dedicated external pins 153 through 156 may be used as externalreference inputs for an ADC external reference inputs and analog supply275. For example, pin 153 may be for a positive reference voltage. Pin154 may be used for a negative reference voltage. Pin 155 may be for anADC supply voltage, AV_(DD). Pin 156 may be for an ADC ground reference,AV_(SS).

With continuing reference to FIG. 2, and additional reference to FIG.3A, an exemplary embodiment of the System Monitor 20 is furtherdescribed. System Monitor 20 is coupled to FPGA internal sensors 203-1to 203-M (“internal sensors 203”), for M a positive integer. Forpurposes of illustration, it is assumed that M is equal to three, thoughfewer or more than three sensors may be used.

Internal sensors 203 are analog sensors. Examples of sensors 203 includetemperature sensors, supply voltage monitor sensors, and supply voltagepeak/sag capture detectors. Notably, though sensor/detectors 203 arereferred to as internal transducers, both external and internaltransducers may be used with System Monitor 20.

External differential analog input channels are provided withdifferential analog input pairs 124 through 127. A differential analoginput pair may be selected for output from multiplexer 214 for input tomultiplexer 216. Analog inputs 124 through 127 may use differentialdigital input/output pairs in a selected input/output portion of a bankof input/output blocks of an FPGA. For example, fourteen local digitalinputs/outputs of an FPGA may be used to provide seven differentialanalog channels. Notably, analog input channels 124 through 127 may beused to monitor FPGA external environmental conditions or physicalcharacteristics, such including without limitation power supply,voltages, currents, temperature of transducers, and chassis integrity.Additionally, dedicated analog inputs 122 and 123 may be provided asinputs to multiplexer 216.

Outputs of internal sensors/detectors 203 are provided as inputs tomultiplexer 217, and one or more of such inputs to multiplexer 217 maybe provided as output for input to multiplexer 216.

Control signals, such as from a channel sequencer 222, for multiplexers214 and 217 monitoring environmental conditions or physicalcharacteristics, may sequentially select channels for input tomultiplexer 216. However, with respect to multiplexer 216, output isselected responsive to control signal 212. Control signal 212 is achannel selection control signal. Accordingly, internal or externalparameters are selected for output for multiplexer 216 as determined byappropriate channel selection in ADC control registers 206. Channelselection signal 212 is responsive to ADC control registers 206.

Output of multiplexer 216 is provided as input to ADC 200. ADC 200receives reference voltage inputs 153 through 156. ADC 200 receivescontrol signal 212, CONVST clock signal 157 and ADC clock signal 219.Output of ADC 200 includes ADC data bus signaling 131 and busy signal135. System Monitor 20 may be located at a bottom of a center column ofan FPGA. Notably, one or more System Monitors may be included in an FPGAsubject to device size limitations. For example, one System Monitor maybe instantiated at a bottom location of a center column of an FPGAhaving one ADC 200 and another ADC may be instantiated at a top locationof the center column of such an FPGA. One input/output bank to a side,such as the left side, of a center column of the FPGA may be used foranalog inputs 124 through 127.

System Monitor 20 may be configured to monitor on-chip environmentalconditions and physical characteristics for self monitoring, and performself-calibration responsive to such self monitoring. System monitor 20may be dynamically configured and controlled via a DRP 201 with signalinputs and outputs as previously described.

ADC 200 may have a resolution of a number of bits and have a specifiedmaximum sampling speed. For example, ADC may have a resolution of 10bits and a maximum sampling speed of 200 kilo-samples per second(“kSPS”). Specifications of ADC 200 relating to System Monitoringinclude measurement accuracy with respect to slowly varying or directcurrent analog input signals, as these signals may be representative ofa monitoring application. For example, in an embodiment having a 10-bitADC, there is a minimum theoretical measurement accuracy of 1 in 1,024counts. Thus, a signal level within an analog input range of such a10-bit ADC may be at least resolved to an accuracy of 0.1%.

However, inaccuracy in transducers, such as resistive attenuation, anderrors in an implementation of an ADC may limit measurement accuracy towithin plus or minus 1%. If a linearity error of an ADC is less than 0.5of one least significant bit (“LSB”), other errors in the ADC andtransducers such as offset error and gain error may be mitigated bydoing post-conversion digital correction. Accordingly, measurementaccuracies with post-conversion digital correction of less than 0.1% maybe obtained.

By using a multiplexer tree 220, the number of ADC analog input channelsmay be increased beyond the number of input channels of ADC 200. Forexample if ADC 200 has one differential input channel provided by inputs211 and 213, by having output of multiplexer 216 coupled to such inputs211 and 213, any of the input channels of multiplexer tree 220 may beselected for output from multiplexer 216 as input to ADC 200. Thoughthree multiplexers are shown for multiplexer tree 220, fewer or moremultiplexers may be used. ADC clock signal 219 may be provided fromcontrol logic 221. Control logic 221 is coupled to receive oscillatorsignal 215 and DRP clock signal 108. Control logic 221 may use a clocksource from DRP clock signal 108 or an internal FPGA oscillator signal215, which is defined by internal FPGA configuration. Additionally, DRPclock signal 108 is provided to DRP interface 205.

Control logic 211 is configured to provide over temperature signal 111and includes circuitry for an IEEE Standard 1149.1 TAP interface 110.Control logic 211 is coupled to System Monitor register memory/interface210. System Monitor register memory/interface 210 includes controlregisters 206 and data registers 209. DRP interface 205 includes amemory controller for reading and writing from and to System Monitormemory 210.

System Monitor register memory/interface 210 further includes DRPinterface 205. DRP interface 205 includes a controller for DRP 201,which is described in the co-pending patent application entitled“Reconfiguration Port for Dynamic Reconfiguration”, by Vasisht M. Vadiet. al., filed concurrently. Notably, System Monitor control logic 221of configuration memory/interface 210 provides channel signal 132, EOCsignal 133, EOS signal 134, alarm signals 137, and over temperaturealarm signal 139.

FIG. 3B is a simplified block diagram of a System Monitor of analternative embodiment of the present invention. The system monitorincludes a microcontroller 2006 such as a hardwired 16-bit PicoBlazefrom Xilinx Corp. of San Jose Calif., a memory 2008 having dataregisters 209 and control registers 206 (see FIG. 4), a channelsequencer 222 (which allows a user to set up a sequence of channels viasequence registers 312 and their associated operating conditions forautomatic monitoring), an ADC 200 (see FIG. 3C), a Calibration block2014 receiving set calibration values such as gain and offset fromcalibration registers 313 (see FIG. 4), a Filter block 2016 may filterdata based on filter parameters set in filter registers 2017, an Alarmblock 2018 using set values from alarm registers 314 to do a comparisonwith monitored values, registers 2020 for general storage of results andInput/Output (I/O) multiplexers 2012 which connect together themicrocontroller 2006, memory 2008, channel sequencer 222, ADC 200,calibration 2014, filter 2016, alarm 2018, and registers 2020.

The 16-bit PicoBlaze is described in PicoBlaze 8-Bit Microcontroller forVirtex-II Series Devices XAPP627 (v1.1) Feb. 4, 2003, and in Appendix A,both of which are incorporated by reference, herein. In one embodimentthe instructions for the 16-bit PicoBlaze are stored in a Programmableread-only memory (PROM) so that the microcontroller can perform thecalibration 2014, filter 2016, and/or alarm 2018 functions independentof the state of the rest of the IC, e.g., FPGA. In another embodimentthe instructions for the 16-bit PicoBlaze are stored in a block RAM(BRAM) on the FPGA such as BRAM 28 of FIG. 1 or BRAM in 44B or 44C ofFIG. 1C.

As FIG. 3B shows there may be in one use of the System Monitor, apipeline flow of data, e.g., the ADC 200 data can be calibrated (viacalibration 2014) using calibration registers 313, then filtered (viafilter 2016), then checked if there should be an alarm (via alarm 2018)by doing a comparison with a set value(s) in alarm registers 314 and theresult of the comparison stored in registers 2020.

FIG. 3C is a block diagram of an ADC 200 of an embodiment of the presentinvention. The track and hold (T&H) block 2100 is described inco-pending patent application, Ser. No. 10/231,541, entitled“Analog-to-Digital Converter which is Substantially Independent ofCapacitor Mismatch” by Patrick J. Quinn, filed Aug. 29, 2002, which isherein incorporated by reference. The algorithmic block 2102 and digitalerror correction block 2104 are described in U.S. Pat. No. 6,642,751 B1,entitled “Configurable Track-and-Hold Circuit” by Patrick J. Quinn,filed Sep. 6, 2002, which is herein incorporated by reference.

FIG. 4 is a block diagram depicting an exemplary embodiment of a memorymap for System Monitor registers 206 and 209 for system monitor registermemory/interface 210. With continuing reference to FIG. 4 and renewedreference to FIGS. 1A through 1E and 2, the memory map is furtherdescribed.

Data registers 209 include data registers 301-1 through 301-N for N apositive integer, temperature maximum register 302, temperature minimumregister 303, VCC auxiliary maximum register 308, VCC auxiliary minimumregister 309, VCC internal maximum register 304, VCC internal minimumregister 305, Vtest maximum register 306, and Vtest minimum register307.

Control registers 206 include configuration registers 310-1 through310-M for M a positive integer, and test registers 311-1 through 311-Pfor P a positive integer. Control registers 206 include sequenceregisters 312-1 through 312-Q for Q positive integer.

Control registers 206 include calibration registers 313-1 through 313-Sfor S a positive integer, alarm registers 314-1 through 314-R for R apositive integer.

By way of example not limitation, data registers 209 and controlregisters 206 may all be 16-bit wide registers. Moreover, by way ofexample, there may be 26 data registers 209 and 64 dynamicallyreconfigurable control registers 206. Control registers 206 may bedynamically reconfigured, such as to select a System Monitor channel andto store alarm threshold values for parameters being monitored, via DRPinterface 205. Control registers 206 may be part of a random accessmemory block, such as a static random access memory block of memory ofan FPGA. This block of memory may be dedicated memory of a functionblock, such as System Monitor 20, or may be dual ported configurationmemory of an FPGA.

Notably, during initialization of an FPGA, default settings for controlregisters 206 may be set to default values as part of a configurationbit stream used to initialize an FPGA. This initialization allows SystemMonitor 20 to start operation in known condition, and facilitates alarmvalues to be stored and downloaded from FPGA configuration memory.

Continuing the above example, a first block of 32 registers of 64control registers 206 includes System Monitor configuration registers310, test registers 311 and channel sequence registers 312. Of the first32 registers, six registers are reserved for configuration and testingof System Monitor 20, such as channel selection and sampling mode, amongother configuration and test settings. Twenty registers of the firstblock of 32 registers are for defining channel selection for a sequencemode. The remaining six registers are unused and are not accessible viaDRP 201.

Again, continuing the above example, the second block of 32 registers ofthe 64 dynamic reconfiguration registers may be used to hold alarmthresholds for digital comparison and calibration of coefficients forFPGA internal sensors. One of these registers may be defined fortemperature sensor offset correction, such as one of test registers 311.

FIG. 5 is a block diagram depicting bit assignments 400 forconfiguration registers 310. Notably, bit locations are somewhatarbitrary. For example, bit locations 401 and 423 may be switched usingsome previously unused bit locations. Moreover, for example, bitlocations 402 through 405 may be swapped with bit locations 411 through413. Additionally, for example, bit locations 411 may be switched withbit locations 412 using a previously unused bit location. Accordingly,it should be understood that bit locations are arbitrary, and bitlocations other than those described below may be used. Configurationregisters 310 may be reserved for System Monitor 20 configuration bits.Continuing the above example, for each configuration register 310, thereare sixteen possible register bit locations in which data may be stored,of which only a portion of the register bit locations are used. Bitlocations 401 of configuration register 310-0 (“configuration register0”) are used to select an analog input channel for ADC 200. A selectedchannel may be for receipt of an FPGA internally monitored parameter,such as voltage or temperature, or for receipt of an externallymonitored parameter, such as output of a transducer external to a SystemMonitor 20 host FPGA. In a sequence mode, a selected channel may bemonitored as a logic output of data bus 131 of ADC 200.

Data bit position 402 is used to increase acquisition time available fora Continuous Sampling Mode by a number, such as four, ADC clock cyclesof ADC clock signal 108. Acquisition time may be increased by settingthis bit for example to a logic one. Data bit position 403 is used toselect either a continuous or an Event Driven Sampling Mode for ADC 200.For example, a logic one places ADC 200 in an Event Driven SamplingMode, and a logic zero places ADC 200 in a Continuous Sampling Mode.Data bit position 404 is used to select either a unipolar or bipolaroperating mode for analog input to ADC 200. For example, a logic oneplaces ADC 200 in a bipolar mode, and a logic zero places ADC 200 in aunipolar mode. Bit positions 405 are used to enable averaging of datasamples for a selected channel or channels. Registers 405 may be set forno averaging or averaging a number of samples, such as 16, 64 and 256.

Configuration register 310-1 (“configuration register 1”) has data bitposition 411 which is used to activate over temperature alarm signal 139when a temperature exceeds a threshold temperature. For example, when atemperature greater than 120 degrees Celsius is detected, overtemperature alarm signal 139 would be enabled by setting data in bitlocation 411 to a logic one value. Bit position 413 of configurationregister 310-1 is used to enable automatic comparison of measuredon-chip parameters, such as voltage and temperature, within limitsdefined in alarm registers 314 of FIG. 4.

Bit positions 412 may be used to enable or disable individual alarmlogic outputs. Contents of alarm registers 314 in FIG. 4 may be mostsignificant bit (“MSB”) justified, and alarm limits may be set using a10-bit transfer function for FPGA internal temperature and voltagesensors.

Bit positions 414 may be used to enable a channel sequencer function.Sequence registers 414 may be used to disable a channel sequencer 222,or to activate a channel sequencer 222 for a one pass through sequenceor for a continuous cycling of a sequence.

Bit positions 422 of configuration register 310-2 may be set to adefault or be used to activate digital calibration of FPGA internalsensors. Calibration registers 422 may be used for setting calibrationon or off, setting ADC digital offset correction, setting a power supplydigital offset correction, or setting both an ADC digital offsetcorrection and a power supply digital offset correction to be active.Calibration registers 313 in FIG. 4 may be used to store calibrationcoefficients used by System Monitor 20. For example, a temperatureoffset correction may be used, an ADC offset correction may be used, anda power supply offset correction may be used.

Bit positions 423 of configuration register 310-2 are used to select adivision ratio of a system clock input signal frequency and a lowerfrequency of ADC clock signal 108. Clock divider registers 423 may beused for dividing a system clock frequency down to a frequency forsynchronization. For example, a DRP clock signal 108 has a maximumfrequency, which for example may be approximately 450 MHz. A systemclock signal for System Monitor 20 may be derived from DRP clock signal108. For example, DRP clock signal 108 may be divided by two to providea system clock signal, which for example may be approximately 225 MHz.However, ADC 200 may have an input clock frequency, namely, thefrequency of ADC clock signal 219, which is substantially less than afrequency of a system clock signal of System Monitor 20. For example,ADC 200 may operate with an ADC clock signal 219 in a frequency range ofapproximately 100 kHz to 2 MHz. ADC clock signal 219 is maintained at orabout a frequency, such as 2 MHz, by dividing down a DRP clock signal108 or on-chip oscillator clock signal 215 frequency. Accordingly,generation of an additional clock signal for System Monitor 20, and moreparticularly ADC 200, may be avoided by dividing down DRP clock signal108 or oscillator clock signal 215 thereby avoiding adding complexity tointerface 205. Clock division registers 423 may be used to divide down asystem clock signal.

By dividing down DRP clock signal 108, a user my select an existingclock signal in a design and use it for System Monitor 20 therebyavoiding a dedicated System Monitor clock signal. In an embodiment,there are a minimum number of system clock signal cycles, such as four,used for each ADC clock signal 219 for some System Monitoring functions,and thus a divider ratio of this minimum number is a minimum.

System monitor 20 may include a temperature sensor 203 that produces avoltage output proportional to temperature of a die of a host FPGA.Output voltage of temperature sensor 203 may be provided by a well-knownequation relating voltage to temperature, charge of an electron andBoltzmann constant. Output voltage of temperature sensor 203 may becoupled to ADC 200 to provide a digital output as part of data busoutput signal 131.

FIG. 6A is a temperature versus output code diagram depicting anexemplary embodiment of an output of ADC 200 for an analog input relatedto temperature. With continuing reference to FIG. 6A and renewedreference to FIGS. 1A through 1E and 2, the output of ADC 200 is furtherdescribed.

Temperature versus ADC digital output 500 is shown as having a stepwisetransfer function 501 going from a least significant bit (“LSB”)generally at 502 for a temperature value at such location to a fullscale transition (“FST”) location generally at 503. Accordingly this isa digital output transfer function for a temperature sensor, such as asensor 203. Additionally, System Monitor 20 may provide a digitalaveraging function allowing the user to average a number of samples, forexample 256 individual temperature sensor samples to produce a reading.Averaging may be used to help reduce the effects of noise and to improverepeatability of measurement. A result of a temperature reading may beplaced in a register of output data registers 209. Notably, a full ADCtransfer function may be greater than a temperature operating range ofan FPGA.

In addition to monitoring temperature, voltage, such as supply voltage,conditions may be monitored for any potential problems. Likewise withrespect to temperature monitoring, monitoring internal power suppliesinvolves selecting a channel via control registers 206. A transferfunction for an on-chip voltage being monitored would be similar to thatof FIG. 6A, namely, having an LSB location and a full scale transitionlocation for a voltage relative to an ADC digital output code. Moreover,voltage monitoring may have a stepwise transfer function for voltageversus ADC digital output code. Signal conditioning in ADC modes mayautomatically be set up responsive to channel selection for a particularsupply voltage being monitored. Notably, there may be more than onesupply voltage on an FPGA. This signal conditioning for ADC 200 modesetup may be done responsive to control signal 212.

In the event an FPGA supply voltage exceeds an input range of adifferential input of ADC 200, an attenuator may be used. To enhanceaccuracy with use of an attenuator without calibration, an externalreference voltage circuit for signal conditioning may be used toaccurately calibrate an ADC 200 for power supply monitoring. Examples ofsuch externally supplied reference voltages include voltages 153, 154,155 and 156.

To capture short duration peaks and sags of voltages such as supplyvoltages, peak detector circuits of sensors 203 may be used. Peak valuesmay be accessed by selecting an associated channel with a peak detector,such as a detector peak detector 203. Again a transfer function similarto that shown in FIG. 6A may be used for detecting peaks and sags.

ADC 200 may be operated in either a Continuous Sampling Mode or an EventDriven Sampling Mode. In a Continuous Sampling Mode, ADC 200automatically starts a new conversion at the end of the currentconversion cycle. In a Continuous Sampling Mode, ADC 200 will continueto carry out a conversion on a currently selected analog input as longas ADC clock signal 219 is present. In an event sampling mode, a userinitiates a next conversion after the end of the current conversioncycle using CONVST signal 116. These operating modes are selected bywriting to ADC configuration register 310-0 location 403, as describedabove.

FIG. 6B is a schematic diagram depicting an exemplary embodiment ofexternal ADC monitoring circuitry 600. An external voltage is used asreference voltage 601 to establish absolute measurement accuracy overextremes of temperature within limits, such as approximately 2.5V±0.2%and ≦50 ppm/° C. With continuing reference to FIG. 6B and renewedreference to FIG. 6A, ADC monitoring circuitry 600 is further described.

Pin 153 is used to receive an external positive reference voltageV_(REFP) to ADC 200. Pin 154 is used to receive an external negativereference voltage V_(REFN) to ADC 200. Pins 155 and 156 are used asanalog voltage supply for ADC 200.

External resistors 602, 603, and 604 are coupled in series to implementan external voltage monitoring circuit. A tap or an output 605 from acommon node of resistors 601 and 602 and a tap or an output 606 from acommon node of resistors 602 and 603 in combination provide adifferential output. This differential output may be provided, such asvia a multiplexer 216, to inputs 211 and 213 of ADC 200.

ADC 200 converts input from pins 211 and 213 into ADC digital outputcode 511. For example, the size of one LSB generally at 502 of an ADCoutput digital code 511 may be approximately 0.977 mV. Theanalog-to-digital transfer function of ADC 200 is inversely proportionalto the external reference voltage V_(IN)/V_(REFN), which for example maybe approximately 2.5V. A change in the reference voltage results in achange in the size of LSB 502. The relationship is inverselyproportional. So, for example, a 1% increase in reference voltage mayresult in maximum of 1% ADC error or less in proportion ofV_(IN)/V_(REFN).

System Monitor Timing Modes.

FIG. 7A is a signal diagram depicting an exemplary embodiment of SystemMonitor start up timing 700. FIG. 7A illustrates power up timing for anFPGA with System Monitor 20 and start up operation of System Monitor 20before FPGA configuration. With continued reference to FIG. 7A andrenewed reference to FIGS. 2 and 3, an embodiment of a start upoperation of System Monitor 20 is further described.

An FPGA chip reset signal (“CFG_RST”) 114 or power on reset (“POR”)signal 771 resets System Monitor logic after FPGA power up. At thispoint in time System Monitor control logic is not operational. SystemMonitor 20 remains in this mode until the end of a “House Keeping” mode721 which may be up to 20 ms or more depending on the size of the FPGAchip. There is no monitoring of any on-chip or off-chip sensors duringHouse Keeping Mode 721. For that mode oscillator clock (“CFG_MCLK”)signal 215 is used by analog circuitry of System Monitor 20 to bring upreference generation circuits and at least one sensor. These circuitsare settled and become fully functioning within specification by the endof House Keeping Mode 721.

Generally at time 711 of oscillator clock signal 215, FPGA configurationlogic issues a logic high initialization complete signal 113 to informSystem Monitor 20 that House Keeping Mode 721 is over. On the nextrising edge, generally at time 712 of oscillator clock signal 215, FPGAconfiguration logic enters a “Fixed Function Mode” 722 for SystemMonitor 20. This is a fixed function mode and thus System Monitor 20operation is completely independent of any activity in configurationmemory cells or programmable interconnect of the host FPGA. Accordingly,System Monitor 20 operation is not affected by changes in configurationbit settings during full or partial configuration/reconfiguration ofCLBs/IOBs of a host FPGA.

During “Fixed Function Mode” 722, System Monitor 20 may measuretemperature for example. If the measured and averaged temperatureexceeds a hardwired limit, such as for example of 110° C., then overtemperature alarm signal 139 is asserted. Over temperature alarm signal139 remains asserted until the measured temperature drops below ahardwired limit, such as for example approximately 70° C. System Monitor20 may average multiple temperatures, such as sixteen temperaturemeasurements, in this mode.

System Monitor 20 leaves “Fixed Function Mode” 722 on a rising edge ofoscillator clock signal 215 after global write enable signal (“GWE_B”)704 goes to a logic low state. Global write enable signal 704 is notde-asserted until after the initial configuration of a host FPGA.Generally at this time 715, System Monitor 20 starts “Normal OperationMode” 723 using the configuration bit stream setting. A dedicated writeconfiguration signal 112 goes logic high responsive to FPGAconfiguration logic writing to FPGA configuration memory. System Monitor20 uses write configuration signal 112 only after the initial power upconfiguration.

FIGS. 7B and 7C are signal diagrams depicting respective exemplaryembodiments of partial configuration mode timings 740 and 750. A usermay implement two types of reconfiguration settings for an FPGA such asNormal Partial Reconfiguration 740 and Active Partial Reconfiguration750.

For Active Partial Reconfiguration 750, FPGA operation is not suspendedand any global signals, such as global write enable signal 704, are notde-asserted and thus the FPGA maintains Normal Operation Mode 723. ForNormal Partial Reconfiguration 740, FPGA operation is suspended andglobal write enable signal 704 is de-asserted.

During Normal Partial Reconfiguration 740, a global write enable signal704 is de-asserted prior to any configuration write operation, such asFixed Function Mode 722, initiated by write configuration signal 112. Aconfiguration write operation, which is in this example Fixed FunctionMode 722, starts by write configuration signal 112. If global writeenable signal 704 is logic high, i.e. is de-asserted, then generally attime 731, System Monitor 20 enters Fixed Function Mode 722 on the nextrising edge of write configuration signal 112.

System Monitor 20 remains in Fixed Function Mode 722 until global writeenable signal 704 is asserted again at the end of the currentconfiguration write operation. Normal operation begins on the firstoscillator clock signal 215 rising edge after global write enable signal704 is asserted, i.e. is logic low signal state, generally at time 734.Notably, write configuration signal 112 may toggle at irregularintervals. However, after the first rising edge of write configurationsignal 112, write configuration signal 112 is not used in the currentmode, and thus subsequent edges of write configuration signal 112 haveno effect on operation of System Monitor 20. System monitor 20 onlyresumes normal operation when global write enable signal 704 transitionsto a logic low signal state.

Because during Active Partial Reconfiguration 750 FPGA operation is notsuspended during configuration, Active Partial Reconfiguration 750 isused for configuration bit scrubbing while configuration bits arecontinuously refreshed.

During Active Partial Reconfiguration mode 750, any global signals likeglobal write enable signal 704 are not de-asserted, i.e., being logichigh, for the duration of the FPGA configuration. Therefore, Systemmonitor 20 does not enter Fixed Function Mode 722 when writeconfiguration signal 112 transitions to logic high and System Monitor 20maintains Normal Operation mode 723 throughout Active PartialReconfiguration 750.

Due to the absence of logic high state for global write enable signal704, Active Partial Reconfiguration 750 may not include a frame whichcontains the System Monitor block. Thus, in this timing mode, SystemMonitor 20 may still be reconfigured via DRP 201.

FIG. 8A is a signal diagram depicting an exemplary embodiment of aContinuous Sampling Mode timing 800. With continuing reference to FIG.8A and renewed reference to FIGS. 1A through 1E and 2, ContinuousSampling Mode timing 800 is further described.

System clock 801 is a fraction of the frequency of data clock 108. Inthis exemplary embodiment, system clock 801 is half the frequency ofdata clock 108. Data write enable signal 107 is pulsed to select achannel for data. For example, pulse 802 having an edge aligned tosystem clock signal 801 is asserted. Responsive to assertion of datawrite enable signal pulse 802, an address 804 on address signal 105 iscaptured along with data. For example, captured address 804 of dataaddress signaling 105 may indicate that data 803 of data input signaling104 is to be written to configuration register 0, which data 803 maysubsequently be output via data output signaling 120 or via DRP 201,which is described in more detail in the co-pending patent application“Reconfiguration Port for Dynamic Reconfiguration”, by Vasisht M. Vadiet. al., filed concurrently.

During an acquisition phase of a Continuous Sampling Mode, ADC 200acquires voltage on a selected channel in order to perform ananalog-to-digital conversion. For example, a capacitor in ADC 200 ischarged to an input voltage for a selected channel. The time to chargethis capacitor will depend on source impedance of the selected inputchannel. Acquisition time may be four cycles of ADC clock signal 219,such as acquisition time 805, namely, from end of a conversion phaseuntil a sampling edge, such as conversion finished edge 807 to asampling edge 806. However, if a new input channel is selected afterstart of an acquisition phase, then acquisition time 805 is from end ofa dynamic reconfiguration port write operation to the sampling edge,namely in this embodiment the fifth rising edge of ADC clock after theend of the previous conversion. If a new channel selection is made bywriting to DRP 201 during a conversion phase, such as conversion time810, namely, after a sampling edge 806 when busy signal 135 is activelogic high, such as pulse 811, a newly selected channel will not startits acquisition phase until the end of a current conversion phase whenbusy signal 135 transitions to a logic low level. In a sequence mode, anew channel selection is made when busy signal goes to a logic low levelvoltage.

If an ACQ bit in a configuration register 0 is set to logic one, then anextra six ADC clock cycles of ADC clock signal 219 are inserted before asampling edge to offer more acquisition time for a selected channel.This may be useful if a sampled signal has a relatively large sourceimpedance, such as greater than approximately 10 kilo-ohms.

A conversion phase starts on a sampling edge, such as sampling edge 806,at the end of an acquisition phase. In other words, after an analogmeasurement is obtained in an acquisition phase, it may then beconverted to a digital value in a conversion phase. From sampling edge806, busy cycle 135 goes to an active logic high state to indicate thatADC 200 is carrying out a conversion. Any channel selection orconfiguration writes to DRP 201 when busy signal 135 is in a logic highstate will not be latched until the end of such a conversion phase,namely, when busy signal 135 goes to a logic low state generally atconversion finished edge 808.

For converting an internal supply voltage monitor channel, an additionalfour ADC clock cycles may be added to a conversion phase. A result of aconversion may appear on ADC data bus 131, such as data 803, at the endof a conversion finished edge, such as edge 808. A conversion resultwill be transferred to data registers 209 one ADC clock cycle after aminimum number of system clock cycles, such as four cycles for example.EOC logic output signal 133 is pulsed high for one pulse width, such aspulse 809, after a conversion phase.

Notably, if a channel being converted is also being filtered, filtereddata will only be transferred to data registers 209 after a last sampleresult has been converted. Thus, if channels are being filtered toprovide an analog-to-digital conversion, no EOC pulse, such as pulse809, will be generated for all such conversions except for a lastconversion result. For example, if 256 samples were taken, the 256^(th)sample would be the sample for which an EOC signal 133 pulse 809 wouldbe generated. Of course the number of samples taken will depend on thefilter setting. When System Monitor 20 is operated in a sequence mode, auser may identify which channel is having data thereon converted bymonitoring channel address signal 132. A channel address of a channelbeing converted is updated responsive to busy signal 135 going to alogic low state at the end of a conversion phase.

Channel address outputs may be used with EOC signal 133 to automaticallylatch contents of output data registers 209 via output data bussignaling 131 to a first-in first-out buffer or block access randommemory. For example, channel output may be associated with a dataaddress where EOC signal 133 is used as a write enable for random accessmemory. If no filtering is being used, EOC signal 133 may be used tolatch contents of ADC data bus signals 131. EOS signal 134 is pushedwhen an output data register for a last channel in a program sequence isupdated.

FIG. 8B is a signal diagram depicting an exemplary embodiment of anEvent Driven Sampling Mode timing 820, and FIG. 8C is a lower-levelsignal diagram depicting an exemplary embodiment of a System Monitordetailed timing 840. Notably, actual values for times t1 through t21 ofFIG. 8C will vary with implementation, and thus are not described hereinin detail.

In Event Driven Sampling Mode, such as even driven sampling mode timing820, sampling and subsequent conversion, is initiated by an internallyor externally triggered signal called Convert Start (“CONVST”) signal157. A logic low to logic high transition (e.g., a rising edge) ofCONVST signal 157 defines a sampling edge for a selected analog inputchannel, such as a sampling edge generally at 821.

CONVST signal 157 may be an asynchronous externally provided signal. Inwhich embodiment, System Monitor 20 automatically resynchronizes aconversion to ADC clock signal 219. CONVST signal 157 has a minimum lowor high time of at least a number of seconds, such approximately 50nanoseconds. As in the above-described Continuous Sampling Mode, ADCclock cycles of ADC clock signal 219 are used for an acquisition phase822, namely, time between a channel change and a sampling edge, such asa rising edge of CONVST signal 157. A sufficient number of ADC clockcycles facilitates ADC 200 to acquire a new signal before it is sampledby CONVST signal 157 and a conversion phase begins.

Notably, the ACQ bit has no meaning in an event sampling mode, since asampling instance is controlled by CONVST signal 157, and thereforeCONVST signal 157 controls acquisition time for a selected channel. If along acquisition time, such as time 822 is used, then a user may leave arequired acquisition time before CONVST signal 157 is pulsed, such as apulse 812.

Notably, as mentioned above, CONVST signal 157 may be provided fromclock inputs such as IOB clocks of an FPGA, namely, global IOB's.Alternatively, CONVST signal 157 may be exercised by an FPGA from aglobal clock network via a local interconnect, namely, CONVST clocksignal 117.

After an analog input has been sampled responsive to a rising edge ofCONVST signal 157, a conversion is initiated on a next rising edge ofADC clock signal 219, such as edge 824. In response, busy signal 135goes to a logic high state. Conversion occurs over a number of clockcycles of ADC clock signal 219. Conversion time 825 is this periodincluding at least a portion of the pulse width of CONVST signal pulse812.

For example for a 10-bit implementation of the above-describedembodiment, when FPGA internal power supply sensors, such as may haveoutputs coupled to input channels of System Monitor 20, are selected, anADC conversion cycle may have 6+n ADC clock cycles. As with a ContinuousSampling Mode, a result of the conversion appears on ADC data bussignaling 131 responsive to busy signal 135 transitioning to a logic lowstate. Such a conversion result will be transferred to data registers209 one ADC clock cycle after a conversion result is obtained with aminimum number of system clock cycles of system clock signal 801, suchas four cycles for example.

EOC signal 133 logic output pulses are transitioned to a logic highstate, such as pulse 826, for one cycle of clock signal 108 for DRP 201after a conversion result is transferred to output data registers 209.If a channel being converted is also being filtered, then filtered datais transferred to output data registers 209 when a last sample resulthas been converted, as previously described. Notably, a rising edgeoccurs on CONVST signal 157 to initiate a conversion and advance asequencer to a next channel. If an automatic sequencing is used, SystemMonitor 20 may be operated in a Continuous Sampling Mode. However, auser may use an event timing mode in a sequence mode. EOC signal 133,EOS signal 134, and channel signal 132 operate as previously describedwith respect to a Continuous Sampling Mode.

System monitor 20 provides a self-contained monitoring function foron-chip supply voltages and temperature. Notably, once System Monitor 20is configured with default settings, only an external DRP clock signal108 resource from a host FPGA is used. Notably, if DRP clock signal 108for DRP 201 is not present, System Monitor 20 automatically switchesover to an on-chip oscillator clock signal 215.

Measurement data for on-chip parameters may be stored in user-readableregisters, namely, registers of data registers 209 of System Monitor 20.Data registers 209 are output data registers which may be accessed viaDRP 201. In addition to collecting measurement data, System Monitor 20may activate alarms, provided via alarm output signal 137, when ameasured data result exceeds a pre-defined threshold value. Thresholdvalues for measurement values, namely, threshold alarm values, arestored in alarm registers 314.

System monitor 20 may be configured to detect over temperatureconditions and both over and under voltage conditions for supplyvoltages. Alarm levels may be user programmable at time of design of acircuit to be instantiated in an FPGA. Furthermore, alarm thresholds maybe dynamically changed via DRP 201.

When an alarm condition is detected, a logic output alarm signal 137automatically goes to an active logic high state. Automatic alarmsignaling may be disabled using System Monitor configuration registersbit location 413 of FIG. 5. Notably, automatic monitoring is provided inpart by a channel sequencer 222, which forms part of control logic 221of FIG. 3A.

Channel sequencer 222 allows a user to set up a sequence of channels andtheir associated operating conditions for automatic monitoring. Asequencer function is made up of a number of channels, includingcalibration channels. For example, there may be approximately 20channels. These channels are associated with registers as previouslydescribed.

Each sequence register may have the same bit definitions asconfiguration register 310-0. Accordingly, as well as selecting achannel, sequence registers may be used to select unipolar ordifferential input operation for that selected channel. Notably,internal channels may be unipolar only. Sequencer 222 may be used toselect whether a channel result is averaged, and may be used to providea longer acquisition time for such a channel. Initially, sequencer 222may be used to select between continuous and event driven modes. As thename implies, sequence registers are read starting at a lowest registeraddress and finishing at the highest register sequence address, or untila sequence register containing all logic ones is encountered.

Sequencer 222 will operate in one of two modes responsive to howsequence bits 414 of configuration registers 310-1 are set. These modesare single pass mode or continuous mode.

In a single pass mode, sequencer 222 completes a measurement on allchannels in a sequence at least once. This may involve a multiplicity ofiterations, such as two hundred fifty six iterations of a sequence, forthose channels having averaging activated. Accordingly, the number ofiterations will depend upon the number of samples taken. When dataregisters of data registers 209 for all channels in a sequence have beenupdated, an EOS signal 134 pulse, such as pulse 826, is issued on a lastdata register update.

At this point, data registers contain results of all channels in asequence. Channels with no averaging will have a corresponding dataregisters overwritten on each pass through a sequence rather than just afinal pass of a sequence. Accordingly, data registers are maintained tocontain the most recent measurement data associated therewith. Busysignal 135 and EOC signal 133 continue to be active duringanalog-to-digital conversions, when System Monitor 20 is operating in asequence mode.

At the end of a sequence, ADC 200 reverts back to configuration definedfor the configuration registers for the next and subsequent conversions.To reset a sequence, a user can reset System Monitor 20 with resetsignal 199. This reset may be done dynamically via DRP 201.

Continuous mode operation is the same as single pass mode operation,except at the end of a singled pass through a sequence, an EOS signal134 pulse is issued, such as pulse 809, and the sequence automaticallystarts over again. Conversion or average results from each selectedchannel in a sequence are loaded into a corresponding data register ofdata registers 209 when a conversion is finished. These registers may beread during operation via DRP 201. For example, results from channel 0may be written to data register 0 and results from channel 5 may bewritten to data register 5, where 0 and 5 refer to address locations ofsuch registers. When EOS signal 134 is pulsed at the end of a sequence,a new sequence automatically starts with data continuously being writtento a data register of data registers 209 by System Monitor 20. To avoidreading a register that is being written to by System Monitor 20, dataregister reads may happen only when busy signal 135 is at a logic highvoltage level. Accordingly, a high speed read of all data registers maybe started when busy signal 135 goes to a logic high voltage level aftera pulse of EOS signal 134. Notably, a result of the channel is writtento data registers even when System Monitor 20 is not operating in asequence mode.

As mentioned above, System Monitor 20 offers the capability of averagingresults, such as 16, 64, or 256 results, among others, of separatemeasurements for a selected channel, for example to reduce effects ofnoise in such results. When averaging is active, noise content ofmeasured quantities like power supply voltage and temperature may besignificantly reduced. Furthermore, by adding hysteresis to suchmeasurements, risk of producing a false alarm condition that mightotherwise exist if such an alarm condition was based on just onemeasurement may be reduced. Furthermore, calibration channels may beaveraged to obtain a more accurate offset correction.

FIG. 9A is a signal diagram depicting another exemplary embodiment of aContinuous Sampling Mode timing 900. With continuing reference to FIG.9A and renewed reference to FIGS. 1A through 1E and 2, ContinuousSampling Mode timing 900 is further described.

In Continuous Sampling Mode 900, ADC 200 continues to carry out aconversion on the currently selected analog inputs as long as ADC clocksignal 219 is present. ADC clock signal 219 is generated by the clockdivider registers 423. The analog-to-digital conversion process isdivided into two parts, namely, acquisition phase 805 and conversionphase 810.

During acquisition phase 805, ADC 200 acquires the voltage on a selectedchannel to perform the conversion. The acquisition phase basicallyinvolves charging a capacitor in ADC 200 to the input voltage on theselected channel. The time required to charge this capacitor depends onthe source impedance of the selected input channel. Acquisition time 805involves a number of ADC clock signal 219 cycles, such as four forexample, from the end of the previous conversion phase until thesampling edge of the next phase. When not operating in sequence mode, auser needs to write to configuration register 310-0 to select the nextchannel for conversion. Write operations to configuration registershappen while busy signal 135 is high.

Configuration register settings are latched when busy signal 135transitions to a logic low signal state. In sequence mode, a new channelselection is made automatically when busy signal 135 transitions to alogic low signal state. If the ACQ bit in configuration register 0 isset to logic one, then a number of extra ADC clock signal 219 cycles,such as six for example, are inserted before the sampling edge to allowfor more acquisition time on a selected channel. This is useful if anexternal analog input channel has a large source impedance, e.g, greaterthan 10 k-ohms. These extra ADC clock signal 219 cycles are 10 through23 (cycles 14 and 20 are not shown on FIG. 9A). For an embodiment, anedge transition time 911 for busy signal 135 may be equal toapproximately 10 ns, and time interval 912 from the instance 907 of edgetransition 911 to pulse 811 of EOC/EOS signal 133/134 may be equal toapproximately 10 clock cycles of system clock signal 801.

Conversion phase 810 starts on sampling edge 806 of busy signal 135 atthe end of acquisition phase 805. Generally at this point in time, busysignal 135 transitions to a logic high state to indicate ADC 200 iscarrying out a conversion. Any channel selection or configuration writesto the DRP 201 when busy signal 135 is logic high is latched until theend of conversion phase 810 (i.e., when busy signal 135 transitions to alogic low signal state). In an embodiment, conversion phase 810 may be13 ADC clock signal 219 cycles in duration. When converting an internalsupply monitor channel, an additional number, such as four for example,of ADC clock signal 219 cycles may be added to the conversion cycle. Theresult of a conversion on an external channel also appears on the ADCdata bus 131 one half of an ADC clock signal 219 cycle before busysignal 135 transitions to a logic low signal state. Conversion resultsfor on-chip sensors may be accessed via data registers 209 via DRP 201.

ADC 200 conversions are transferred to the data registers a number, suchas 10 for example, of cycles of system clock 801 after the end of aconversion responsive to busy signal 135 transitioning to a logic lowsignal state. The logic output of EOC signal 133 will pulse high for oneDRP clock cycle at this time. If the channel being converted is alsobeing filtered, then the filtered data will only be transferred to theoutput data registers when the last sample result is converted. Thus, ifa channel is being filtered, no pulse of EOC signal 133 will begenerated for all but the last conversion result i.e., 16th, 64th, 256thsample depending on the filter setting. When System Monitor 20 is beingoperated in a sequence mode, a user may identify which channel is beingconverted by monitoring channel signal 132 addresses. A channel addressof a channel being converted may be updated on these logic outputs halfan ADC clock signal 219 cycle before busy signal 135 transitions to alogic low signal state at the end of a conversion phase 810.

Channel address logic outputs 132 may be used with EOC signal 133 toautomatically latch the contents of the output data registers into aFIFO or BRAM, such as by connecting channel address logic outputs 132 todata addressing 105 and using EOC signal 133 as a write enable for theBRAM. If no filtering is being used then EOC signal 133 may also be usedto latch the contents of the ADC data bus 131. EOS signal 134 has thesame timing as EOC signal 133. EOS signal 134 is pulsed when the outputdata register for the last channel in a programmed sequence is updated.

FIG. 9B is a signal diagram depicting another exemplary embodiment of anEvent Driven Sampling Mode timing 920, and FIG. 9C is a lower-levelsignal diagram depicting another exemplary embodiment of a SystemMonitor detailed timing 940. Notably, actual values for times t1 throught14 of FIG. 9C will vary with implementation, and thus are not describedherein in detail.

In Event Driven Sampling Mode 920, as in Event Driven Sampling Mode 820of FIG. 8B, sampling and subsequent conversion are initiated by aninternally or externally triggered signal. CONVST signal 157 may be usedfor this triggering.

In Event Driven Sampling Mode 920, a sampling instant and subsequentconversion process is initiated by an internal or external trigger, suchas CONVST signal 157. A logic low to logic high transition (rising edge)on CONVST signal 157, such as rising edge 921 of pulse 912, defines ansampling instant for a selected analog input channel. Busy signal 135transitions to a logic high state just before the sampling instant.Signal CONVST 157 may be an asynchronous external signal, as SystemMonitor 20 automatically re-synchronizes a conversion to ADC clocksignal 219. A restriction on CONVST signal 157 is that it has a minimumlow or high time, for example a minimum low or high time of at least 50ns. As for Continuous Sampling Mode 900, enough time is provided foracquisition phase 922 ranging between a channel change and a samplingedge, i.e. the rising edge 921 of pulse 912 for CONVST signal 157. Thisallows ADC 200 to acquire a new signal before it is sampled by CONVSTsignal 157 and before a conversion phase 925 starts following theacquisition phase 922.

Notably, ACQ bit 402 has no meaning in event sampling mode 920 since thesampling instant is controlled by CONVST signal 157 and therefore so isthe acquisition time on the selected channel. If a long acquisition timeis to be used, then acquisition time before CONVST signal 157 is pulsedis provided. After an analog input has been sampled by a rising edge onCONVST signal 157, a conversion is initiated on the next rising edge ofADC clock signal 219. In Event Driven Sampling Mode 920, ADC 200 uses anumber of ADC clock cycles of ADC clock signal 219 (for example 12cycles marked 1 through 12 on FIG. 9B though pulses 3 through 10 are notshown), to perform a conversion, such as a 10-bit conversion forexample. When FPGA on-chip power supply sensors are selected, an ADC 200conversion cycle may be extended, for example by 6 additional (16 total)ADC clock signal 219 cycles.

As with Continuous Sampling Mode 900, the result of the conversion on anexternal channel also appears on the ADC data bus 131 one half ADC clocksignal 219 cycles before busy signal 135 transitions to a logic lowsignal state. The conversion result may also be transferred to theoutput data registers a number of system clock cycles 912 later, such as10 clock cycles later for example. EOC signal 135 logic output pulses toa logic high state, such as pulse 926, for one DRP clock signal 108cycle at this time. If the channel being converted is also beingfiltered, then the filtered data will only be transferred to the outputdata registers when the last sample result has been converted. Thus, ifa channel is being filtered, no EOC pulse 135 is generated for all butthe last conversion result, i.e. 16th, 64th, 256th sample depending onthe filter setting. If the automatic sequencer is being used, SystemMonitor 20 may operate in Continuous Sampling Mode 900. However, if auser wishes to use Event Timing Mode 920 in a sequence mode, this timingis allowed. EOC 135, EOS 136, and channel outputs 134 operate the sameway described above for Continuous Sampling Mode 900 of FIG. 9A.

System Monitor Configurations

FIG. 10 is a block/schematic diagram depicting an exemplary embodimentof a portion of System Monitor 20 with averaging. With continuousreference to FIG. 10 and renewed reference to FIGS. 1A through 1E andFIGS. 2, 3 and 4, System Monitor 20 averaging operation is furtherdescribed.

On-chip measurement may be averaged using averagers 1005-1 through1005-Z, for Z a positive integer. For example, there may beapproximately thirteen averagers 1005. Averagers 1005 may be a part ofADC 200 or a part of register memory/interface 210.

ADC clock signal 219 is applied to each averager 1005 and to ADC 200.Measurement samples from dedicated analog inputs 122, 123 or userselectable external analog inputs 124 through 127 may be provided to ADC200 via one or more of multiplexers 214 and 216. Analog-to-digitalconverted samples are output from ADC 200 and provided to averagers1005. Output signal 1006 from sequence registers 207 of sequencer 222 isused as a control signal input to multiplexer 216 to select a channelsample for input to ADC 200.

Additionally, ADC 200 includes voltage references, such as a shortcircuit channel input 156 and a positive reference voltage channel input153, shown in FIG. 3A, which may be averaged. Averaging for a selectedchannel is activated by writing data settings to bit locations 405 ofconfiguration register 310-0.

When operating in a sequence mode, successive samples are taken fromdifferent channels in the sequence even if an averaging function hasbeen activated on some other channels. An averager of a channel may beupdated once per each single pass through sequence registers 207.Accordingly, average values for a given channel may be computed over alonger time frame than taking successive samples on a selected channelfor averaging. A result is loaded from an averager 1005 into output dataregisters 209. Additionally, offsets may be calibrated using averaging,and thus if a selected channel is used for calibration, output from anaverager 1005 is provided to a respective calibration register 313.

Once a predetermined number of samples have been collected, an averager1005 is reset to zero. Notably, sequencer 222 may be activated ordeactivated by writing to sequence bit locations 414 of configurationregister 310-1. Responsive to sequencer 222 being activated ordeactivated, averaging accumulators are reset to zero via sequencerreset signal 1004. Channel selection is done by providing a controlsignal 1006 from sequence registers 207 to a select input of multiplexer216. An ADC configuration signal 1008 may be provided from sequenceregisters 207 to ADC 200 to configure ADC 200. Additional input to ADC200 may come from control registers 206 as depicted by FIG. 4.

A user may use an averaging function when not operating in a sequencemode. In such a condition, an average is computed using successivesamples from a selected channel. An EOC signal 133 pulse is issued afteran average result is loaded into output data registers 209.

System monitor 20 may be configured to automatically generate alarmsignals when measured quantities exceed predetermined maximum or minimumlevels. Apart from the over temperature register, such limits are heldin alarm registers 314 in System Monitor memory 210. Over temperatureregister contents are defined by configuration bit settings which arenot accessible via DRP 201.

Alarm conditions may be generated for on-chip parameters liketemperature, and power supply voltage. An alarm may be indicated in oneof a plurality, such as eight, alarm signals, such as seven alarmsignals 137 and over-temperature alarm signal 138. An alarm condition isgenerated based on contents of data registers 209. If data averaging isactivated, an average value will be used in order to generate an alarmcondition. Notably, temperature measurement may be used to initiate anover temperature alarm, and averaging may be used to provide such anover-temperature alarm to reduce or avoid impact of erroneoustemperature measurements.

FIG. 11 is a block diagram depicting an exemplary embodiment of aportion of System Monitor 20 having a digital comparator 1101. Outputsfrom data registers 209 and alarm registers 314 are provided as inputsto comparator 1101. Notably, in this embodiment for each data registerthere is a corresponding alarm register. Comparator 1101 may determinewhether a data register value is larger or smaller than an alarmregister value. Output of comparator 1101 are over temperature alarmsignal 139, over temperature signal 111, which is a direct connection toconfiguration logic of an FPGA, and alarm signals 137. Alarm signals, aswell as over temperature alarm signal 139, are connect to a host FPGAvia local interconnects.

Notably, individual alarm logic outputs may be disabled by setting alarmbits, such as over temperature register bit 411 and alarm register bits412, to a logic zero in configuration register 310-1. Moreover, anautomatic alarm function, except for over temperature alarm signals 139and over temperature signal 111, may be disabled by setting alarm bit412 in configuration register 310-1 to logic zero.

Output logic alarms 137 are not activated responsive to a measuredparameter, such as contents of output data registers 209, being withintolerance as specified in alarm registers 314. Output data registers 209may be configured to allow maximum or minimum measurement fortemperature and power supply voltages to be captured as part ofmonitored channels. Each temperature and supply voltage channel has anassociated maximum and minimum register. For example, temperature, VCCinternal, and VCC auxiliary have associated maximum and minimum registerstarting addresses.

A currently measured value, such as temperature or power supply voltage,may be compared with contents of its maximum and minimum registers. If acurrently held value exceeds a value in a maximum register, the maximumregister is updated along with a current value register to reflect thecurrent value. Similarly, for a minimum register, if a current valuefalls below minimum register contents, then the minimum register isupdated to reflect the current value. A current value may be obtainedfrom ADC 200, as an average number of samples. Again, a user may set thenumber of samples for averaging. Reset input signal 199 may be used toreset contents of maximum and minimum registers for temperature andsupply voltages. Responsive to a reset, maximum registers may be set tologic zero and minimum registers may be set to a full scale value, asdescribed above with respect to a transfer function.

Accuracy of ADC 200 transfer function is dependent on measurementaccuracy. For measuring parameters, direct current accuracy of ADC 200depends upon offset, gain and linearity errors, among otherspecifications. Accordingly, a user may carry out an offset calibrationof ADC 200 to enhance accuracy of ADC 200.

Offset calibration may be done by digitally adding or subtracting anoffset correction from an ADC conversion result. An offset correctionfactor may be obtained when a conversion is carried out in a bipolarmode with differential inputs of an analog channel to ADC 200 shorted.For a channel having analog inputs shorted selected foranalog-to-digital conversion, a user may opt to have averaging of thisdata by setting bits 405 in configuration register 310-0. A number ofdifferent measurements or samples may be used for this averaging, aspreviously described, to obtain an average ADC offset. An offsetcorrection factor may be stored in a non-user accessible register.Notably, there is no output data register 209 for a short-circuitedchannel, and use of an offset calibration coefficient is activated byusing calibration bits 422 in configuration register 310-2. Ashort-circuited input channel may further be inserted into a sequenceregister just like any other channel. By inserting a short-circuitedinput channel into a sequence register 207, continuous background ADCoffset calibration may be done during operation, namely, a continuousoffset calibration.

System monitor 20 provides calibration for removing offset in on-chippower supply voltage sensors, such as sensors for VCC internal, and VCCauxiliary. An offset correction factor is obtained when a conversion iscarried out with a channel selection set to an auxiliary supply voltage,VCC auxiliary, connected to a positive reference voltage, V_(REFP). Whena channel is selected for conversion, a user has an option of averagingdata by setting averaging bits 405 in configuration register 310-0. Thenumber of samples collected to calculate an average offset formonitoring supply voltages may be varied, as previously describedherein. An offset is calculated by comparing an average measurementresult on a selected channel with an ideal result for a supply voltage,such as approximately 2.5 volts for an auxiliary supply voltage, VCCauxiliary. Accordingly, this depends on a reference voltage supplyhaving a narrow tolerance, such as within approximately plus or minus0.2%. Such an offset correction factor may be stored in a non-useraccessible register.

Notably, there is no output data register 209 for a positive referencevoltage channel. Use of an offset calibration coefficient is activatedby using calibration bits 422 in configuration register 310-2. Apositive reference voltage input channel may further be inserted into asequencer 222 just like any other channel. Such insertion would be forcontinuous background offset calibration over temperature and time, asan external voltage reference will be stable with changes in integratedcircuit die temperature.

An on-chip temperature sensor provides a voltage output proportional totemperature. For example, a targeted uncalibrated temperature error ofsuch a sensor may be approximately plus or minus 4 degrees Celsius.Signal conditioning circuitry may be used to level shift and amplify atemperature sensor voltage to match it to an analog input range of ADC200. However, if a more accurate measurement of temperature is to beused, a one-point calibration at a known temperature may be done.

FIG. 12 is a block/schematic diagram depicting a single pointtemperature calibration circuit 1200. Temperature sensor 1202 haspositive and negative voltage outputs, a differential output, coupled toa differential input of ADC 200. Output of ADC 200 is a digital output,which may be provided to a summing junction 1201 for summing with anoffset correction 1203. Offset correction 1203 may be stored in acalibration register 313 as described above.

Output 1204 from summing junction 1201 is an ADC code adjusted forcorrection offset. An offset correction 1203 is digitally added orsubtracted from an ADC result. This offset correction may be in additionto an ADC offset correction previously mentioned. A temperature offsetcorrection register may be accessed by a user via DRP 201 for access toa calibration register 313. A calibration register 313 may contain aninitial value, which may be used after characterization of an FPGA dye,which may be used to center a transfer function of temperature sensor1202. Notably, users may modify contents of such a calibration registerin order to carry out their own calibration.

Notably, many registers have no definition in any ADC mode. Accordingly,such registers may be used as user memory for a processor, such as anembedded or software instantiated microprocessor, which controls ADC 200function. Accordingly, writing to such user registers will have noimpact on operation of ADC 200. Such scratch registers may be read andwritten via DRP 201 and may be initialized at design time or dynamicallyreconfigured during operation. Notably, a user may disable calibrationcoefficients at any time by using calibration bits 422 in configurationregisters 310-2.

Analog inputs of ADC 200 may employ differential sampling to reduceeffects of common mode noise signals. Common mode rejection improvesperformance of ADC 200 in noisy digital environments. ADC 200 analoginputs may be driven from single-ended or differential sources. Forusing analog inputs with single-ended sources unipolar mode should beused. For driving analog inputs from a differential source, such analoginputs are used in a bipolar mode. Unipolar and bipolar mode selectionis made by writing to unipolar/bipolar mode bit location 404 inconfiguration register 310-0.

FIGS. 13A and 13B are schematic diagrams depicting exemplary embodimentsof respective unipolar and bipolar mode analog inputs to ADC 200. Inboth unipolar mode and bipolar mode, each terminal 122 and 123 isrespectively coupled to a multiplexer having a resistance 1301.Operation of multiplexer 216 may be modeled as a sampling switch 1311having an associated sampling capacitance, such as sampling capacitor1303 in a unipolar mode and sampling capacitors 1304 and 1305 in abipolar mode. Sampling switch 1311 and associated sampling capacitanceare used to acquire signal of an analog input for conversion by ADC 200.

During an acquisition phase, sampling switch 1311 is closed and asampling capacitance, such as for sampling capacitor 1303 or samplingcapacitors 1304 and 1305, is charged up to voltage of an analog input.Time needed to charge such a capacitor to a final value is dependentupon the capacitor capacitance as well as the multiplexer resistance.For example, with a multiplexer having a resistance of approximately 100ohms for a dedicated analog channel, or approximately 30 kilo-ohms foran auxiliary analog channel, and sample capacitance of approximately sixpico-farads in a unipolar mode and approximately three pico-farads in abipolar mode, acquisition time may be in the nanosecond range fordedicated connections and in the sub-one microsecond range for auxiliaryanalog input channels. Accordingly, external resistance of analog inputsadds to the effective impedance, shown as multiplexer resistance, forpurposes of determining acquisition time.

Output coding of ADC 200 in a unipolar mode is binary. Design codetransitions occur at successive integer LSB values.

When operated in a bipolar mode, analog inputs to ADC 200 may be drivenfrom differential sources. When an input is differential, the amplitudeof such an input is the difference between the positive and negativevoltage inputs. A peak-to-peak amplitude of each input is approximatedto a common mode voltage. For a differential source, common mode voltageis defined as the quantity of a positive voltage plus a negative voltagedivided by two. Output coding of ADC 200 in bipolar mode is two'scompliment. Accordingly, design code transitions occur at successiveinteger LSB values.

System monitor 20 is integrated into a host FPGA. This integrationincludes access to local interconnect tiles, clock resources,configuration memory, dedicated input/output lines and local digitalinput/output connections for additional analog inputs. Additionally,IEEE Standard 1149.1-controlled read-back support for System Monitor 20output data registers may be included.

FIGS. 14A and 14B are block diagrams depicting respective exemplaryembodiments of System Monitor floor plans 1420 and 1440. Notably,interconnect tiles 1401 may be connected to IOBs 1410 via traces 1411 ineach System Monitor floor plan 1420 and 1440.

In System Monitor floor plan 1420, eight interconnect tiles 1401 borderSystem Monitor dynamic reconfiguration memory 1402 and programmableread-only memory 1403. System monitor logic block 1404 borders SystemMonitor dynamic reconfiguration memory 1402 and a portion ofprogrammable read-only memory 1403. Notably, programmable read-onlymemory 1403 within System Monitor 20 is optional, and may be omitted ifinsufficient area is available. In which embodiment, memory external toSystem Monitor 20 may be accessed. System monitor analog block 1405borders System Monitor logic block 1404 and a portion of programmableread-only memory 1403. System monitor analog block 1405 includes ADC200, analog multiplexers, reference voltage generators, temperaturesensors, peak detectors, and supply voltage monitors.

In System Monitor floor plan 1440, the interconnect tiles 1401 borderSystem Monitor dynamic reconfiguration memory 1442, System Monitor logicblock 1444 and a portion of System Monitor analog block 1445. Systemmonitor dynamic reconfiguration memory 1442 and System Monitor logicblock 1444 border System Monitor analog block 1445. System monitoranalog block 1445 includes ADC 200, analog multiplexers, referencevoltage generators, temperature sensors, and supply voltage monitors.

System monitor logic block 1444 includes a processor block 1449.Processor block 1449 may include an embedded microprocessor, such as a16-bit hardwired version of a PicoBlaze from Xilinx, Inc. of San Jose,Calif., or an embedded microsequencer. Memory whether internal to orexternal from System Monitor 20 may be used to store instructions forsuch an embedded processor or microsequencer.

DRP clock signal 108 for DRP 201 is obtained directly from an FPGAinterconnect tile and used to clock ADC 200. Additionally, DRP clocksignal 108 for DRP 201 is used to clock digital logic and synchronizeddata transfers between System Monitor 20 and other FPGA circuitry.

DRP clock signal 108 is not derived from an on-chip oscillator signal215. On-chip oscillator signal 215 may automatically switched over as asource clock for System Monitor 20 internal circuitry in the event thereis no DRP clock signal 108 input from an FPGA interconnect. DRP clocksignal 108 may be derived from an externally provided signal to a hostFPGA.

On-chip oscillator signal 215 source is used during an initial power-upand is provided to run System Monitor 20 for temperature monitoringuntil DRP clock signal 108 takes over, if present. System monitor 20transitions to use DRP clock signal 108, if present, responsive toglobal write enable signal 704 going to a logic low level and DRP clocksignal 108 becoming active at the end of an FPGA initial configurationof System Monitor 20.

System monitor 20 switches over to signal 215 during power-down of anFPGA and continues to monitor FPGA conditions, such as temperature,during power-down. System monitor 20 is configured to detect if DRPclock signal 108 from an FPGA interconnect somehow goes missing duringoperation, and will switch over to on-chip oscillator signal 215 toprovide continued monitoring. Selection of on-chip oscillator signal 215is controlled by System Monitor control logic 221.

FIG. 15A is a schematic diagram depicting an exemplary embodiment ofSystem Monitor 20 clock tree 1500. Clock tree 1500 includes multiplexers115 and 1508, and optionally may include inverter 1505. Multiplexer 115may be made up of multiplexers 1502, 1503 and 1504. With renewedreference to FIGS. 2 and 3 and continued reference to FIG. 15A, clocktree 1500 is further described.

CONVST clock input 157 is used for an event-sampling mode to define asampling incident of ADC 200. CONVST clock signal 157 has three possiblesources. CONVST clock signal 157 may be obtained from a clock outputfrom an interconnect, namely, CONVST clock signal 117. CONVST clocksignal 157 may be obtained from a logic output from an interconnect,namely, CONVST signal 116. Or, CONVST clock signal 157 may be obtainedfrom one of a number, such as sixteen, of GIOB clock signals 118 whichare differential.

GIOB clock signals 118 provide a low jitter, low latency clock sourcefor CONVST clock signal 157. For an ADC 200 sampling clock in dynamicapplications, it is beneficial to have limited jitter.

For example, CONVST clock multiplexer 1502 may receive sixteen GIOBclock signal inputs 118 of which one may be selected for output frommultiplexer 1502. A control signal, such as FPGA configuration bitssignal 1530, may be used to select one of GIOB clock signal inputs 118for output from multiplexer 1502. Output of multiplexer 1502 is providedas an input to multiplexer 1504.

Multiplexer 1503 receives a CONVST clock signal 117 and a CONVST signal116. A control signal, such as FPGA configuration bits signal 1530, maybe used to select one of CONVST clock signal 117 and CONVST signal 116for output from multiplexer 1503. Output of multiplexer 1503 is providedas an input to multiplexer 1504.

Output of multiplexer 1504 is either one of CONVST clock signal 117 andCONVST signal 116 or one of GIOB clocks 118. A control signal, such asFPGA configuration bits signal 1530, may be used to select an outputfrom multiplexer 1504. The output of multiplexer 1504 is CONVST signal157. The output from multiplexer 1504 may be inverted with an optionalinverter 1505 to provide CONVSTOUT signal 140. CONVST clock multiplexers1502, 1503 and 1504 may be implemented in System Monitor 20.

Dynamic reconfiguration port DRP clock signal 108 and on-chip oscillatorsignal 215 are provided as inputs to multiplexer 1508. System monitorcontrol logic 221 provides a control signal 1540 to multiplexer 1508 toselect DRP clock signal 108 when present and to select on-chiposcillator signal 215 when DRP clock signal 108 is not present toprovide ADC data clock signal 1541. Data clock signal 1541 is divideddown to provide ADC clock signal 219.

System monitor 20 initializes control via registers 310, 312, 313 and314. Registers 310, 312, 313 and 314 may be written to and read from byFPGA both during an initialization as well as afterwards dynamicallyduring operation. However, to initialize registers 310, 312, 313 and 314at design time, such registers may be associated with FPGA configurationmemory cells as a memory block. A dynamic reconfiguration memory blockmay be used to implement System Monitor 20 registers 310, 312, 313 and314.

Configuration register bits for System Monitor 20 may be implementedusing dynamic reconfiguration. Thus, in addition to being configured bya configuration bitstream, such bits may be read to and written fromFPGA fabric via DRP 201. Address space is allocated for reading andwriting to such registers via DRP 201.

System Monitor JTAG Configurations

FIG. 15B is a block diagram depicting an exemplary embodiment of an FPGA10, 50, and 60 having a System Monitor 20, configuration memory 1518,system memory 1512, processor 30, oscillator 1552, and an IEEE 1149.1TAP controller 1517. System Monitor 20 may communicate via DRP 201 toaccess configuration memory 1518 associated with System Monitor 20.System Monitor 20 includes a system monitor digital bus 180.

With renewed reference to FIGS. 2, 3 and 15A and continued reference toFIG. 15B, FPGAs 10, 50, and 60 are further described. Aspects of SystemMonitor 20 configuration are not accessible via DRP 201 including a bitused to divide DRP clock signal 108 to provide a state machine clocksignal. Additionally, there are bits for dividing down oscillator signal215 to provide ADC clock signal 219. There are bits to set overtemperature alarm limits, and these bits have the same definition asbits in alarm registers 314. There are bits used to configure operatingmodes of System Monitor 20, including system monitor mode, ADC mode,test mode, and system monitor block power-off, among other parameters orfunctions for operating modes. There are bits used to select a CONVSTclock source.

There are bits used as block enables for hardwired logic in SystemMonitor 20. Each of these blocks may be disabled and their functionalityreplaced with a software instantiated processor. The default setting isto disable a software instantiated processor. There are bits used toactivate adjustments to system monitor functionality.

A number of dedicated connections between configuration logic block andSystem Monitor blocks may be present. These dedicated connections may beused to provide JTAG read functionality to data registers 209. Specialpurpose and global signals allow System Monitor 20 to operate beforeconfiguration and during partial configuration of an FPGA.

Output registers of System Monitor 20 may be scanned via an IEEE 1149.1Test Access Port (“TAP”) as part of TAP controller 1517. A TAPcontroller state machine of IEEE 1149.1 TAP controller 1517 containsinstructions to allow a read-back of output data stored in output dataregisters 209 via a Test Data Out (“TDO”) bus of the TAP controller1517. A read-back may be done during an FPGA power-down or after aninitial power-up of an FPGA prior to configuration of System Monitor 20.Scan pins 141 through 150 may be used by TAP controller 1517 to doboundary test scans of System Monitor 20.

TAP controller 1517 is a digital interface, which may conform to IEEE1149.1. Accordingly, it should be understood that by using ADC 200functions to provide digital signals to TAP controller 1517, TAPcontroller 1517 may be used to provide analog test capability using anIEEE 1149.1 interface. This is done in part by using ADC 200 of SystemMonitor 20, and thus circuitry overhead for analog testing is reduced.Additionally, as described below in additional detail, adigital-to-analog converter (“DAC”) may be added to a boundary-scanchain to provide an analog stimulus for a test procedure for aparametric analog test of a component.

FIG. 16A is a block diagram depicting an exemplary embodiment of SystemMonitor 20 TAP signal connections 1600 for the register memory/interface210. FIG. 16B is a signal diagram depicting an exemplary embodiment ofSystem Monitor read timing 1670. With simultaneous reference to FIGS.16A and 16B, System Monitor TAP signal connectivity and read timing isfurther described.

Output data registers 209 are coupled to shift register 1601 forproviding stored data thereto. Stored data is shifted out of shiftregister 1601 via test data output (“TDO”) signals 1602. An addresscounter 1603 is coupled to output data registers 209. Capture dataregister signal 1604, enable signal 1605 and clock data register signal1606 are provided to shift register 1601 and address counter 1603. Clockdata register signal 1606 may be provided responsive to and synchronizedwith a Test Clock (“TCLK”) signal 1640.

For a readback of output data stored in output data registers 209,System Monitor 20 shifts out a header sequence 1620, such as 32 zeros,of TDO signals 1602 to synchronize external clock TCLK 1640 withinternal System Monitor clock 108. Furthermore, this shifting out of 32zeros provides sufficient time for System Monitor 20 to suspend updatingof output data registers 209 and start shifting registers contents outonto TDO signals 1602. Data 1621 is shifted out starting at a 33^(rd)clock cycle, generally at 1610, of data register clock signal 1606. Data1621 continues to be shifted out ending with an ending clock cycle, suchas clock cycle 416 of clock data register signal 1606 generally at 1611.

Accordingly, on TDO signals 1602 a header 1620, such as of 32 zeros, isfollowed by data 1621 from output data registers 209. In the exemplaryembodiment illustratively shown in FIG. 16B, if capture data registersignal 1604 is high on a rising edge of clock data register signal 1606,the first zero is shifted out on the next clock data register signal1606 rising edge, generally at 1632. This idle time (e.g., 32 zeros) isused to provide enough time for System Monitor 20 to suspend updating ofoutput data registers and start shifting output data register contentsout via TDO signals 1602. Data is shifted out starting with the MostSignificant Bit (“MSB”) of one data register, such as a first registerin a stack, and ends with the Least Significant Bit (“LSB”) of anotherdata register, such as a last register in the stack. In this embodiment,data is shifted out starting at clock cycle 33 and ending on clock cycle416.

In addition to monitoring on-chip quantities like temperature andvoltage, System Monitor 20 provides access to external analog signalsvia existing digital input/output blocks of an FPGA. These digitalinput/output blocks may be defined either as digital or analog inconfiguration at the time of configuration of an FPGA. In an embodiment,input/output bank to the left of center column 83 of FIG. 1D may be usedto provide seven differential input channels (i.e., auxiliary analoginput channels) for seven external auxiliary input/output channels.Differential analog input channels may be routed for impedance matchingto enhance analog performance.

In an embodiment, System Monitor 20 includes six dedicated input/outputsto ADC 200. Two of these dedicated input/outputs are for a differentialinput. Two other of these input/outputs are for a differential referencevoltage input. By using an external reference device, positive andnegative reference voltages with low temperature coefficients may besupplied. Accordingly, such a reference voltage should be stable over awide temperature range, as it will be used to calibrate on-chipmeasurements. The remaining two analog input/outputs coupled todedicated connections of an FPGA are ADC VDD 155 and ADC VSS 156, andmay be used to decouple the power supply for ADC 200 analog circuits andprovide a ground return for ADC digital circuitry.

FIG. 16C is a signal diagram depicting an exemplary alternativeembodiment of System Monitor read timing 1670A. System Monitor readtiming 1670A is similar to System Monitor read timing 1670 of FIG. 16B,except clock data register signal 1606 begins and ends at a logic highlevel; enable signal 1605 is shifted one clock cycle of TCLK 1640 to theright; and capture data register signal 1604 is shifted one clock cycleof TCLK 1640 to the right. Thus, clock data register signal 1606 will beat a logic high level when not used as described below.

Responsive to JTAG instruction for System Monitor access being loadedand the JTAG state machine being taken through a capture data register(“CaptureDR”) state to a shift data register (“ShiftDR”) state, clockdata register signal 1606 begins cycling, namely, going to a logic lowlevel for a half cycle and then to a logic high level for a half cycleand then repeating the cycle. Capture data register signal 1604 pulseshigh during that first full cycle 1675 that clock data register signal1606 goes from an idle logic high state to cycling. Enable signal 1605in response to pulse 1631 goes to a logic high level on the falling edgeof that first full cycle 1675 of clock data register signal 1606.

FIG. 17A is a block/schematic diagram depicting an exemplary embodimentof an analog-to-digital TAP interface 1700 for capturing data. Controllogic 1701 is configured to provide TDO signals 1602 and to receivecaptured data register signal 1604, clock data register signal 1606 andTest Data Input (“TDI”) signals 1702. Signals 1604, 1606, 1602 and 1702are to or from JTAG controller 1517 of FIG. 15B.

A channel for inputting data is selected from multiplexer 216 aspreviously described, and such data is provided to ADC 200 foranalog-to-digital conversion. ADC 200 may be configured by control logic1701. Output of ADC 200 is stored in data registers 209 under control ofcontrol logic 1701.

For example, with a JTAG write operation, an internal or external sensorto a host FPGA may be selected by sending an address for channelselection to control logic 1701 and thereby to analog multiplexer 216. Asubsequent JTAG write operation may be used to instruct ADC 200 viacontrol logic 1701 to perform an analog-to-digital conversion on analogoutput from a selected channel and place the digital result in aregister of data registers 209. A subsequent JTAG read operation may beused to access the digital result.

FIG. 17B is a block/schematic diagram depicting an exemplary embodimentof a digital-to-analog JTAG interface 1710. Digital-to-analog converter(“DAC”) 1712 is coupled to receive digital input from control logic1711. Control logic 1711 is coupled to JTAG controller 1517 of FIG. 15Bto receive digital TDI signals 1702 and configured to provide digitalTDI signals 1702 to DAC 1712. DAC 1712 converts such TDI digital inputto analog output and is coupled to provide a differential analog outputto demultiplexer 1716. Demultiplexer 1716 may be multiplexer 216 of FIG.17A operated in a reverse direction. Moreover, multiplexer 216 of FIG.17A and demultiplexer 1716 may be thought of as a multiplexer tree, suchas multiplexer tree 220 of FIG. 3A, where the latter is operated in thereverse direction.

A control signal from control logic 1711 is used to select a channelfrom a plurality of channels 1714 to provide differential analog output,for example to a detector, sensor or other circuit or network under test1713. For example, an analog voltage may be provided to circuit undertest 1713. Circuit under test 1713 may be external or internal to a hostFPGA of interface 1710.

For example, a write-only function may be implemented allowing DAC 1712output voltage to be adjusted using a JTAG write operation.Demultiplexer 1716 may be used to select a circuit to be tested.Notably, by using a demultiplexer 1716, a single DAC may be used to testmultiple circuits. Output of DAC 1712 may be a reference voltage,frequency or waveform for testing analog functions of circuit under test1713.

In FIGS. 17A and 17B, control logic 1711 and 1702 may be formed ofconfigurable logic. However, control logic 1711 and 1702 may behardwired logic. Moreover, multiplexer 216 and demultiplexer 1716 areformed of hardwired logic. Notably, an analog input may be provided viaDAC 1712 to a circuit under test 1713, and the response to such analoginput stimulus may be an analog voltage or other analog information.This information may be collected using a TAP of TAP controller 1517 ofFIG. 15B. Collected information may be monitored by System Monitor 20 ofFIG. 2. For such monitoring, an analog output response may be convertedto digital information using ADC 200. Accordingly, analog components ofa circuit under test 1713 may be determined. Thus, analogcharacteristics of a circuit under test 1713 may be evaluated for analogtrim or calibration. Moreover, TAP controller 1517 of FIG. 15B may beused to collect responses to analog stimuli for system level analogcalibration for production testing.

Accordingly, it should be appreciated that an ADC and DAC embedded in ahost FPGA for use in mixed signal applications may be leveraged forcalibration and test using JTAG circuitry of such a host FPGA. This isnot limited to FPGA integrated circuits, but includes other integratedcircuits. For example, microcontrollers may include an embedded ADC andsupport JTAG for testing and to program embedded memory, such asembedded flash memory. Such an integrated circuit may have the ADC addedto the boundary-scan chain, where an analog interface of themicrocontroller may be used to perform analog measurements with chip orboard level data being available via a an IEEE 1149.1 interface duringtesting. For example, at a circuit board level, power supply voltages,current and temperatures may be monitored over a digital test bus, suchas a JTAG interface, using an ADC for an analog-to-digital conversion ofthe monitored signals. Notably, external channels do not have to bededicated, but may be assigned to applications, such as a userinterface, e.g., touch screen, among other applications. Furthermore,prior to swapping in a replacement circuit board, TAP controller 1517may be used to test analog functionality of such board, as well asdigital functionality, prior to using it as a replacement.

Furthermore, it should be appreciated that by using or reusing embeddedDAC or ADC functionality within an FPGA, tests may be run that wouldotherwise involve using more expensive Automated Test Equipment (“ATE”).For example, with a programmable logic device, such as a CPLD or FPGA,post processing of digital information converted from analog informationmay be done internal to such programmable logic device by downloadingBuilt-In Self-Test (“BIST”) functions, such as Fast Fourier Transforms(“FFTs”), using configurable logic. By configuring configurable logicand programmable interconnects, a mixed signal tester on an integratedcircuit may be provided with a programmable logic device so configured.

While the foregoing describes exemplary embodiment(s) in accordance withone or more aspects of the invention, other and further embodiment(s) inaccordance with the one or more aspects of the invention may be devisedwithout departing from the scope thereof, which is determined by theclaim(s) that follow and equivalents thereof. Claim(s) listing steps donot imply any order of the steps. Trademarks are the property of theirrespective owners. Additionally, the headings herein are for theconvenience of the reader and are not intended to limit the scope of oneor more aspects of the invention.

1. A method of system monitoring, comprising: providing a system monitorhaving registers accessible via a reconfiguration port; and dynamicallyreconfiguring at least one of the registers via the reconfiguration portto select a channel to be monitored by the system monitor; the systemmonitor including an analog-to-digital converter; wherein thedynamically reconfiguring is performed while operating theanalog-to-digital converter.
 2. The method, according to claim 1,wherein the channel is selected by providing a channel select signal toa multiplexer.
 3. The method, according to claim 2, wherein themultiplexer output is coupled to an analog-to-digital converter input ofthe analog-to-digital converter.
 4. The method, according to claim 3,wherein the at least one register is a dual ported memory, the dualported memory being configuration memory of a programmable logic device.5. The method, according to claim 3, wherein the at least one registeris a random access memory, the random access memory being block memoryof a programmable logic device.
 6. The method, according to claim 5,further comprising setting default values for the system monitorresponsive to a configuration bit stream used to initialize theprogrammable logic device.